35252 Commits

Author SHA1 Message Date
Peter Zijlstra
d2098b4440 rcu,ftrace: Fix ftrace recursion
Kim reported that perf-ftrace made his box unhappy. It turns out that
commit:

  ff5c4f5cad33 ("rcu/tree: Mark the idle relevant functions noinstr")

removed one too many notrace qualifiers, probably due to there not being
a helpful comment.

This commit therefore reinstates the notrace and adds a comment to avoid
losing it again.

[ paulmck: Apply Steven Rostedt's feedback on the comment. ]
Fixes: ff5c4f5cad33 ("rcu/tree: Mark the idle relevant functions noinstr")
Reported-by: Kim Phillips <kim.phillips@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-11-19 19:37:17 -08:00
Joe Perches
7c47ee5aa0 rcu/tree: Make struct kernel_param_ops definitions const
These should be const, so make it so.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-11-19 19:37:17 -08:00
Joel Fernandes (Google)
9f866dac94 rcu/tree: Add a warning if CPU being onlined did not report QS already
Currently, rcu_cpu_starting() checks to see if the RCU core expects a
quiescent state from the incoming CPU.  However, the current interaction
between RCU quiescent-state reporting and CPU-hotplug operations should
mean that the incoming CPU never needs to report a quiescent state.
First, the outgoing CPU reports a quiescent state if needed.  Second,
the race where the CPU is leaving just as RCU is initializing a new
grace period is handled by an explicit check for this condition.  Third,
the CPU's leaf rcu_node structure's ->lock serializes these checks.

This means that if rcu_cpu_starting() ever feels the need to report
a quiescent state, then there is a bug somewhere in the CPU hotplug
code or the RCU grace-period handling code.  This commit therefore
adds a WARN_ON_ONCE() to bring that bug to everyone's attention.

Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
Suggested-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-11-19 19:37:16 -08:00
Neeraj Upadhyay
a3941517fc rcu: Clarify nocb kthreads naming in RCU_NOCB_CPU config
This commit clarifies that the "p" and the "s" in the in the RCU_NOCB_CPU
config-option description refer to the "x" in the "rcuox/N" kthread name.

Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>
[ paulmck: While in the area, update description and advice. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-11-19 19:37:16 -08:00
Neeraj Upadhyay
ed73860cec rcu: Fix single-CPU check in rcu_blocking_is_gp()
Currently, for CONFIG_PREEMPTION=n kernels, rcu_blocking_is_gp() uses
num_online_cpus() to determine whether there is only one CPU online.  When
there is only a single CPU online, the simple fact that synchronize_rcu()
could be legally called implies that a full grace period has elapsed.
Therefore, in the single-CPU case, synchronize_rcu() simply returns
immediately.  Unfortunately, num_online_cpus() is unreliable while a
CPU-hotplug operation is transitioning to or from single-CPU operation
because:

1.	num_online_cpus() uses atomic_read(&__num_online_cpus) to
	locklessly sample the number of online CPUs.  The hotplug locks
	are not held, which means that an incoming CPU can concurrently
	update this count.  This in turn means that an RCU read-side
	critical section on the incoming CPU might observe updates
	prior to the grace period, but also that this critical section
	might extend beyond the end of the optimized synchronize_rcu().
	This breaks RCU's fundamental guarantee.

2.	In addition, num_online_cpus() does no ordering, thus providing
	another way that RCU's fundamental guarantee can be broken by
	the current code.

3.	The most probable failure mode happens on outgoing CPUs.
	The outgoing CPU updates the count of online CPUs in the
	CPUHP_TEARDOWN_CPU stop-machine handler, which is fine in
	and of itself due to preemption being disabled at the call
	to num_online_cpus().  Unfortunately, after that stop-machine
	handler returns, the CPU takes one last trip through the
	scheduler (which has RCU readers) and, after the resulting
	context switch, one final dive into the idle loop.  During this
	time, RCU needs to keep track of two CPUs, but num_online_cpus()
	will say that there is only one, which in turn means that the
	surviving CPU will incorrectly ignore the outgoing CPU's RCU
	read-side critical sections.

This problem is illustrated by the following litmus test in which P0()
corresponds to synchronize_rcu() and P1() corresponds to the incoming CPU.
The herd7 tool confirms that the "exists" clause can be satisfied,
thus demonstrating that this breakage can happen according to the Linux
kernel memory model.

   {
     int x = 0;
     atomic_t numonline = ATOMIC_INIT(1);
   }

   P0(int *x, atomic_t *numonline)
   {
     int r0;
     WRITE_ONCE(*x, 1);
     r0 = atomic_read(numonline);
     if (r0 == 1) {
       smp_mb();
     } else {
       synchronize_rcu();
     }
     WRITE_ONCE(*x, 2);
   }

   P1(int *x, atomic_t *numonline)
   {
     int r0; int r1;

     atomic_inc(numonline);
     smp_mb();
     rcu_read_lock();
     r0 = READ_ONCE(*x);
     smp_rmb();
     r1 = READ_ONCE(*x);
     rcu_read_unlock();
   }

   locations [x;numonline;]

   exists (1:r0=0 /\ 1:r1=2)

It is important to note that these problems arise only when the system
is transitioning to or from single-CPU operation.

One solution would be to hold the CPU-hotplug locks while sampling
num_online_cpus(), which was in fact the intent of the (redundant)
preempt_disable() and preempt_enable() surrounding this call to
num_online_cpus().  Actually blocking CPU hotplug would not only result
in excessive overhead, but would also unnecessarily impede CPU-hotplug
operations.

This commit therefore follows long-standing RCU tradition by maintaining
a separate RCU-specific set of CPU-hotplug books.

This separate set of books is implemented by a new ->n_online_cpus field
in the rcu_state structure that maintains RCU's count of the online CPUs.
This count is incremented early in the CPU-online process, so that
the critical transition away from single-CPU operation will occur when
there is only a single CPU.  Similarly for the critical transition to
single-CPU operation, the counter is decremented late in the CPU-offline
process, again while there is only a single CPU.  Because there is only
ever a single CPU when the ->n_online_cpus field undergoes the critical
1->2 and 2->1 transitions, full memory ordering and mutual exclusion is
provided implicitly and, better yet, for free.

In the case where the CPU is coming online, nothing will happen until
the current CPU helps it come online.  Therefore, the new CPU will see
all accesses prior to the optimized grace period, which means that RCU
does not need to further delay this new CPU.  In the case where the CPU
is going offline, the outgoing CPU is totally out of the picture before
the optimized grace period starts, which means that this outgoing CPU
cannot see any of the accesses following that grace period.  Again,
RCU needs no further interaction with the outgoing CPU.

This does mean that synchronize_rcu() will unnecessarily do a few grace
periods the hard way just before the second CPU comes online and just
after the second-to-last CPU goes offline, but it is not worth optimizing
this uncommon case.

Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-11-19 19:37:16 -08:00
Frederic Weisbecker
e3771c850d rcu: Implement rcu_segcblist_is_offloaded() config dependent
This commit simplifies the use of the rcu_segcblist_is_offloaded() API so
that its callers no longer need to check the RCU_NOCB_CPU Kconfig option.
Note that rcu_segcblist_is_offloaded() is defined in the header file,
which means that the generated code should be just as efficient as before.

Suggested-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-11-19 19:37:16 -08:00
chao
dfe564045c rcu: Panic after fixed number of stalls
Some stalls are transient, so that system fully recovers.  This commit
therefore allows users to configure the number of stalls that must happen
in order to trigger kernel panic.

Signed-off-by: chao <chao@eero.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-11-19 19:37:16 -08:00
Peter Zijlstra
6dbce04d84 rcu: Allow rcu_irq_enter_check_tick() from NMI
Eugenio managed to tickle #PF from NMI context which resulted in
hitting a WARN in RCU through irqentry_enter() ->
__rcu_irq_enter_check_tick().

However, this situation is perfectly sane and does not warrant an
WARN. The #PF will (necessarily) be atomic and not require messing
with the tick state, so early return is correct.  This commit
therefore removes the WARN.

Fixes: aaf2bc50df1f ("rcu: Abstract out rcu_irq_enter_check_tick() from rcu_nmi_enter()")
Reported-by: "Eugenio Pérez" <eupm90@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-11-19 19:34:17 -08:00
Jakub Kicinski
56495a2442 Merge https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2020-11-19 19:08:46 -08:00
Linus Torvalds
4d02da974e Networking fixes for 5.10-rc5, including fixes from the WiFi (mac80211),
can and bpf (including the strncpy_from_user fix).
 
 Current release - regressions:
 
  - mac80211: fix memory leak of filtered powersave frames
 
  - mac80211: free sta in sta_info_insert_finish() on errors to avoid
              sleeping in atomic context
 
  - netlabel: fix an uninitialized variable warning added in -rc4
 
 Previous release - regressions:
 
  - vsock: forward all packets to the host when no H2G is registered,
            un-breaking AWS Nitro Enclaves
 
  - net: Exempt multicast addresses from five-second neighbor lifetime
         requirement, decreasing the chances neighbor tables fill up
 
  - net/tls: fix corrupted data in recvmsg
 
  - qed: fix ILT configuration of SRC block
 
  - can: m_can: process interrupt only when not runtime suspended
 
 Previous release - always broken:
 
  - page_frag: Recover from memory pressure by not recycling pages
               allocating from the reserves
 
  - strncpy_from_user: Mask out bytes after NUL terminator
 
  - ip_tunnels: Set tunnel option flag only when tunnel metadata is
                present, always setting it confuses Open vSwitch
 
  - bpf, sockmap:
    - Fix partial copy_page_to_iter so progress can still be made
    - Fix socket memory accounting and obeying SO_RCVBUF
 
  - net: Have netpoll bring-up DSA management interface
 
  - net: bridge: add missing counters to ndo_get_stats64 callback
 
  - tcp: brr: only postpone PROBE_RTT if RTT is < current min_rtt
 
  - enetc: Workaround MDIO register access HW bug
 
  - net/ncsi: move netlink family registration to a subsystem init,
              instead of tying it to driver probe
 
  - net: ftgmac100: unregister NC-SI when removing driver to avoid crash
 
  - lan743x: prevent interrupt storm on open
 
  - lan743x: fix freeing skbs in the wrong context
 
  - net/mlx5e: Fix socket refcount leak on kTLS RX resync
 
  - net: dsa: mv88e6xxx: Avoid VLAN database corruption on 6097
 
  - fix 21 unset return codes and other mistakes on error paths,
    mostly detected by the Hulk Robot
 
 Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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Merge tag 'net-5.10-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

Pull networking fixes from Jakub Kicinski:
 "Networking fixes for 5.10-rc5, including fixes from the WiFi
  (mac80211), can and bpf (including the strncpy_from_user fix).

  Current release - regressions:

   - mac80211: fix memory leak of filtered powersave frames

   - mac80211: free sta in sta_info_insert_finish() on errors to avoid
     sleeping in atomic context

   - netlabel: fix an uninitialized variable warning added in -rc4

  Previous release - regressions:

   - vsock: forward all packets to the host when no H2G is registered,
     un-breaking AWS Nitro Enclaves

   - net: Exempt multicast addresses from five-second neighbor lifetime
     requirement, decreasing the chances neighbor tables fill up

   - net/tls: fix corrupted data in recvmsg

   - qed: fix ILT configuration of SRC block

   - can: m_can: process interrupt only when not runtime suspended

  Previous release - always broken:

   - page_frag: Recover from memory pressure by not recycling pages
     allocating from the reserves

   - strncpy_from_user: Mask out bytes after NUL terminator

   - ip_tunnels: Set tunnel option flag only when tunnel metadata is
     present, always setting it confuses Open vSwitch

   - bpf, sockmap:
      - Fix partial copy_page_to_iter so progress can still be made
      - Fix socket memory accounting and obeying SO_RCVBUF

   - net: Have netpoll bring-up DSA management interface

   - net: bridge: add missing counters to ndo_get_stats64 callback

   - tcp: brr: only postpone PROBE_RTT if RTT is < current min_rtt

   - enetc: Workaround MDIO register access HW bug

   - net/ncsi: move netlink family registration to a subsystem init,
     instead of tying it to driver probe

   - net: ftgmac100: unregister NC-SI when removing driver to avoid
     crash

   - lan743x:
      - prevent interrupt storm on open
      - fix freeing skbs in the wrong context

   - net/mlx5e: Fix socket refcount leak on kTLS RX resync

   - net: dsa: mv88e6xxx: Avoid VLAN database corruption on 6097

   - fix 21 unset return codes and other mistakes on error paths, mostly
     detected by the Hulk Robot"

* tag 'net-5.10-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net: (115 commits)
  fail_function: Remove a redundant mutex unlock
  selftest/bpf: Test bpf_probe_read_user_str() strips trailing bytes after NUL
  lib/strncpy_from_user.c: Mask out bytes after NUL terminator.
  net/smc: fix direct access to ib_gid_addr->ndev in smc_ib_determine_gid()
  net/smc: fix matching of existing link groups
  ipv6: Remove dependency of ipv6_frag_thdr_truncated on ipv6 module
  libbpf: Fix VERSIONED_SYM_COUNT number parsing
  net/mlx4_core: Fix init_hca fields offset
  atm: nicstar: Unmap DMA on send error
  page_frag: Recover from memory pressure
  net: dsa: mv88e6xxx: Wait for EEPROM done after HW reset
  mlxsw: core: Use variable timeout for EMAD retries
  mlxsw: Fix firmware flashing
  net: Have netpoll bring-up DSA management interface
  atl1e: fix error return code in atl1e_probe()
  atl1c: fix error return code in atl1c_probe()
  ah6: fix error return code in ah6_input()
  net: usb: qmi_wwan: Set DTR quirk for MR400
  can: m_can: process interrupt only when not runtime suspended
  can: flexcan: flexcan_chip_start(): fix erroneous flexcan_transceiver_enable() during bus-off recovery
  ...
2020-11-19 13:33:16 -08:00
Jakub Kicinski
e6ea60bac1 Merge https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf
Alexei Starovoitov says:

====================
1) libbpf should not attempt to load unused subprogs, from Andrii.

2) Make strncpy_from_user() mask out bytes after NUL terminator, from Daniel.

3) Relax return code check for subprograms in the BPF verifier, from Dmitrii.

4) Fix several sockmap issues, from John.

* https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf:
  fail_function: Remove a redundant mutex unlock
  selftest/bpf: Test bpf_probe_read_user_str() strips trailing bytes after NUL
  lib/strncpy_from_user.c: Mask out bytes after NUL terminator.
  libbpf: Fix VERSIONED_SYM_COUNT number parsing
  bpf, sockmap: Avoid failures from skb_to_sgvec when skb has frag_list
  bpf, sockmap: Handle memory acct if skb_verdict prog redirects to self
  bpf, sockmap: Avoid returning unneeded EAGAIN when redirecting to self
  bpf, sockmap: Use truesize with sk_rmem_schedule()
  bpf, sockmap: Ensure SO_RCVBUF memory is observed on ingress redirect
  bpf, sockmap: Fix partial copy_page_to_iter so progress can still be made
  selftests/bpf: Fix error return code in run_getsockopt_test()
  bpf: Relax return code check for subprograms
  tools, bpftool: Add missing close before bpftool net attach exit
  MAINTAINERS/bpf: Update Andrii's entry.
  selftests/bpf: Fix unused attribute usage in subprogs_unused test
  bpf: Fix unsigned 'datasec_id' compared with zero in check_pseudo_btf_id
  bpf: Fix passing zero to PTR_ERR() in bpf_btf_printf_prepare
  libbpf: Don't attempt to load unused subprog as an entry-point BPF program
====================

Link: https://lore.kernel.org/r/20201119200721.288-1-alexei.starovoitov@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2020-11-19 12:26:10 -08:00
Luo Meng
2801a5da5b fail_function: Remove a redundant mutex unlock
Fix a mutex_unlock() issue where before copy_from_user() is
not called mutex_locked.

Fixes: 4b1a29a7f542 ("error-injection: Support fault injection framework")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Luo Meng <luomeng12@huawei.com>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Link: https://lore.kernel.org/bpf/160570737118.263807.8358435412898356284.stgit@devnote2
2020-11-19 11:58:16 -08:00
Daniel Xu
6fa6d28051 lib/strncpy_from_user.c: Mask out bytes after NUL terminator.
do_strncpy_from_user() may copy some extra bytes after the NUL
terminator into the destination buffer. This usually does not matter for
normal string operations. However, when BPF programs key BPF maps with
strings, this matters a lot.

A BPF program may read strings from user memory by calling the
bpf_probe_read_user_str() helper which eventually calls
do_strncpy_from_user(). The program can then key a map with the
destination buffer. BPF map keys are fixed-width and string-agnostic,
meaning that map keys are treated as a set of bytes.

The issue is when do_strncpy_from_user() overcopies bytes after the NUL
terminator, it can result in seemingly identical strings occupying
multiple slots in a BPF map. This behavior is subtle and totally
unexpected by the user.

This commit masks out the bytes following the NUL while preserving
long-sized stride in the fast path.

Fixes: 6ae08ae3dea2 ("bpf: Add probe_read_{user, kernel} and probe_read_{user, kernel}_str helpers")
Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/21efc982b3e9f2f7b0379eed642294caaa0c27a7.1605642949.git.dxu@dxuuu.xyz
2020-11-19 11:56:16 -08:00
Ionela Voinescu
fa50e2b452 sched/topology: Condition EAS enablement on FIE support
In order to make accurate predictions across CPUs and for all performance
states, Energy Aware Scheduling (EAS) needs frequency-invariant load
tracking signals.

EAS task placement aims to minimize energy consumption, and does so in
part by limiting the search space to only CPUs with the highest spare
capacity (CPU capacity - CPU utilization) in their performance domain.
Those candidates are the placement choices that will keep frequency at
its lowest possible and therefore save the most energy.

But without frequency invariance, a CPU's utilization is relative to the
CPU's current performance level, and not relative to its maximum
performance level, which determines its capacity. As a result, it will
fail to correctly indicate any potential spare capacity obtained by an
increase in a CPU's performance level. Therefore, a non-invariant
utilization signal would render the EAS task placement logic invalid.

Now that we properly report support for the Frequency Invariance Engine
(FIE) through arch_scale_freq_invariant() for arm and arm64 systems,
while also ensuring a re-evaluation of the EAS use conditions for
possible invariance status change, we can assert this is the case when
initializing EAS. Warn and bail out otherwise.

Suggested-by: Quentin Perret <qperret@google.com>
Signed-off-by: Ionela Voinescu <ionela.voinescu@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20201027180713.7642-4-ionela.voinescu@arm.com
2020-11-19 11:25:47 +01:00
Ionela Voinescu
31f6a8c0a4 sched/topology,schedutil: Wrap sched domains rebuild
Add the rebuild_sched_domains_energy() function to wrap the functionality
that rebuilds the scheduling domains if any of the Energy Aware Scheduling
(EAS) initialisation conditions change. This functionality is used when
schedutil is added or removed or when EAS is enabled or disabled
through the sched_energy_aware sysctl.

Therefore, create a single function that is used in both these cases and
that can be later reused.

Signed-off-by: Ionela Voinescu <ionela.voinescu@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Quentin Perret <qperret@google.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lkml.kernel.org/r/20201027180713.7642-2-ionela.voinescu@arm.com
2020-11-19 11:25:47 +01:00
Dietmar Eggemann
480a6ca2dc sched/uclamp: Allow to reset a task uclamp constraint value
In case the user wants to stop controlling a uclamp constraint value
for a task, use the magic value -1 in sched_util_{min,max} with the
appropriate sched_flags (SCHED_FLAG_UTIL_CLAMP_{MIN,MAX}) to indicate
the reset.

The advantage over the 'additional flag' approach (i.e. introducing
SCHED_FLAG_UTIL_CLAMP_RESET) is that no additional flag has to be
exported via uapi. This avoids the need to document how this new flag
has be used in conjunction with the existing uclamp related flags.

The following subtle issue is fixed as well. When a uclamp constraint
value is set on a !user_defined uclamp_se it is currently first reset
and then set.
Fix this by AND'ing !user_defined with !SCHED_FLAG_UTIL_CLAMP which
stands for the 'sched class change' case.
The related condition 'if (uc_se->user_defined)' moved from
__setscheduler_uclamp() into uclamp_reset().

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Yun Hsiang <hsiang023167@gmail.com>
Link: https://lkml.kernel.org/r/20201113113454.25868-1-dietmar.eggemann@arm.com
2020-11-19 11:25:47 +01:00
Tal Zussman
b19a888c1e sched/core: Fix typos in comments
Signed-off-by: Tal Zussman <tz2294@columbia.edu>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20201113005156.GA8408@charmander
2020-11-19 11:25:46 +01:00
Valentin Schneider
b5b217346d sched/topology: Warn when NUMA diameter > 2
NUMA topologies where the shortest path between some two nodes requires
three or more hops (i.e. diameter > 2) end up being misrepresented in the
scheduler topology structures.

This is currently detected when booting a kernel with CONFIG_SCHED_DEBUG=y
+ sched_debug on the cmdline, although this will only yield a warning about
sched_group spans not matching sched_domain spans:

  ERROR: groups don't span domain->span

Add an explicit warning for that case, triggered regardless of
CONFIG_SCHED_DEBUG, and decorate it with an appropriate comment.

The topology described in the comment can be booted up on QEMU by appending
the following to your usual QEMU incantation:

    -smp cores=4 \
    -numa node,cpus=0,nodeid=0 -numa node,cpus=1,nodeid=1, \
    -numa node,cpus=2,nodeid=2, -numa node,cpus=3,nodeid=3, \
    -numa dist,src=0,dst=1,val=20, -numa dist,src=0,dst=2,val=30, \
    -numa dist,src=0,dst=3,val=40, -numa dist,src=1,dst=2,val=20, \
    -numa dist,src=1,dst=3,val=30, -numa dist,src=2,dst=3,val=20

A somewhat more realistic topology (6-node mesh) with the same affliction
can be conjured with:

    -smp cores=6 \
    -numa node,cpus=0,nodeid=0 -numa node,cpus=1,nodeid=1, \
    -numa node,cpus=2,nodeid=2, -numa node,cpus=3,nodeid=3, \
    -numa node,cpus=4,nodeid=4, -numa node,cpus=5,nodeid=5, \
    -numa dist,src=0,dst=1,val=20, -numa dist,src=0,dst=2,val=30, \
    -numa dist,src=0,dst=3,val=40, -numa dist,src=0,dst=4,val=30, \
    -numa dist,src=0,dst=5,val=20, \
    -numa dist,src=1,dst=2,val=20, -numa dist,src=1,dst=3,val=30, \
    -numa dist,src=1,dst=4,val=20, -numa dist,src=1,dst=5,val=30, \
    -numa dist,src=2,dst=3,val=20, -numa dist,src=2,dst=4,val=30, \
    -numa dist,src=2,dst=5,val=40, \
    -numa dist,src=3,dst=4,val=20, -numa dist,src=3,dst=5,val=30, \
    -numa dist,src=4,dst=5,val=20

Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Link: https://lore.kernel.org/lkml/jhjtux5edo2.mognet@arm.com
2020-11-19 11:25:46 +01:00
Daniel Jordan
406100f3da cpuset: fix race between hotplug work and later CPU offline
One of our machines keeled over trying to rebuild the scheduler domains.
Mainline produces the same splat:

  BUG: unable to handle page fault for address: 0000607f820054db
  CPU: 2 PID: 149 Comm: kworker/1:1 Not tainted 5.10.0-rc1-master+ #6
  Workqueue: events cpuset_hotplug_workfn
  RIP: build_sched_domains
  Call Trace:
   partition_sched_domains_locked
   rebuild_sched_domains_locked
   cpuset_hotplug_workfn

It happens with cgroup2 and exclusive cpusets only.  This reproducer
triggers it on an 8-cpu vm and works most effectively with no
preexisting child cgroups:

  cd $UNIFIED_ROOT
  mkdir cg1
  echo 4-7 > cg1/cpuset.cpus
  echo root > cg1/cpuset.cpus.partition

  # with smt/control reading 'on',
  echo off > /sys/devices/system/cpu/smt/control

RIP maps to

  sd->shared = *per_cpu_ptr(sdd->sds, sd_id);

from sd_init().  sd_id is calculated earlier in the same function:

  cpumask_and(sched_domain_span(sd), cpu_map, tl->mask(cpu));
  sd_id = cpumask_first(sched_domain_span(sd));

tl->mask(cpu), which reads cpu_sibling_map on x86, returns an empty mask
and so cpumask_first() returns >= nr_cpu_ids, which leads to the bogus
value from per_cpu_ptr() above.

The problem is a race between cpuset_hotplug_workfn() and a later
offline of CPU N.  cpuset_hotplug_workfn() updates the effective masks
when N is still online, the offline clears N from cpu_sibling_map, and
then the worker uses the stale effective masks that still have N to
generate the scheduling domains, leading the worker to read
N's empty cpu_sibling_map in sd_init().

rebuild_sched_domains_locked() prevented the race during the cgroup2
cpuset series up until the Fixes commit changed its check.  Make the
check more robust so that it can detect an offline CPU in any exclusive
cpuset's effective mask, not just the top one.

Fixes: 0ccea8feb980 ("cpuset: Make generate_sched_domains() work with partition")
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20201112171711.639541-1-daniel.m.jordan@oracle.com
2020-11-19 11:25:45 +01:00
Peter Zijlstra
1293771e43 sched: Fix migration_cpu_stop() WARN
Oleksandr reported hitting the WARN in the 'task_rq(p) != rq' branch
of migration_cpu_stop(). Valentin noted that using cpu_of(rq) in that
case is just plain wrong to begin with, since per the earlier branch
that isn't the actual CPU of the task.

Replace both instances of is_cpu_allowed() by a direct p->cpus_mask
test using task_cpu().

Reported-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Debugged-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
2020-11-19 11:25:45 +01:00
Valentin Schneider
d707faa64d sched/core: Add missing completion for affine_move_task() waiters
Qian reported that some fuzzer issuing sched_setaffinity() ends up stuck on
a wait_for_completion(). The problematic pattern seems to be:

  affine_move_task()
      // task_running() case
      stop_one_cpu();
      wait_for_completion(&pending->done);

Combined with, on the stopper side:

  migration_cpu_stop()
    // Task moved between unlocks and scheduling the stopper
    task_rq(p) != rq &&
    // task_running() case
    dest_cpu >= 0

    => no complete_all()

This can happen with both PREEMPT and !PREEMPT, although !PREEMPT should
be more likely to see this given the targeted task has a much bigger window
to block and be woken up elsewhere before the stopper runs.

Make migration_cpu_stop() always look at pending affinity requests; signal
their completion if the stopper hits a rq mismatch but the task is
still within its allowed mask. When Migrate-Disable isn't involved, this
matches the previous set_cpus_allowed_ptr() vs migration_cpu_stop()
behaviour.

Fixes: 6d337eab041d ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()")
Reported-by: Qian Cai <cai@redhat.com>
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/lkml/8b62fd1ad1b18def27f18e2ee2df3ff5b36d0762.camel@redhat.com
2020-11-19 11:25:45 +01:00
Frederic Weisbecker
6775de4984 context_tracking: Only define schedule_user() on !HAVE_CONTEXT_TRACKING_OFFSTACK archs
schedule_user() was traditionally used by the entry code's tail to
preempt userspace after the call to user_enter(). Indeed the call to
user_enter() used to be performed upon syscall exit slow path which was
right before the last opportunity to schedule() while resuming to
userspace. The context tracking state had to be saved on the task stack
and set back to CONTEXT_KERNEL temporarily in order to safely switch to
another task.

Only a few archs use it now (namely sparc64 and powerpc64) and those
implementing HAVE_CONTEXT_TRACKING_OFFSTACK definetly can't rely on it.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20201117151637.259084-5-frederic@kernel.org
2020-11-19 11:25:42 +01:00
Frederic Weisbecker
9f68b5b74c sched: Detect call to schedule from critical entry code
Detect calls to schedule() between user_enter() and user_exit(). Those
are symptoms of early entry code that either forgot to protect a call
to schedule() inside exception_enter()/exception_exit() or, in the case
of HAVE_CONTEXT_TRACKING_OFFSTACK, enabled interrupts or preemption in
a wrong spot.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20201117151637.259084-4-frederic@kernel.org
2020-11-19 11:25:42 +01:00
Hui Su
aabe19b827
nsproxy: use put_nsproxy() in switch_task_namespaces()
We already have a dedicated helper that handles reference count
checking so stop open-coding the reference count check in
switch_task_namespaces() and use the dedicated put_nsproxy() helper
instead.
Take the change to fix a whitespace issue too.

Signed-off-by: Hui Su <sh_def@163.com>
[christian.brauner@ubuntu.com: expand commit message]
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Link: https://lore.kernel.org/r/20201115180054.GA371317@rlk
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2020-11-19 10:57:02 +01:00
Thomas Gleixner
b996544916 tick: Get rid of tick_period
The variable tick_period is initialized to NSEC_PER_TICK / HZ during boot
and never updated again.

If NSEC_PER_TICK is not an integer multiple of HZ this computation is less
accurate than TICK_NSEC which has proper rounding in place.

Aside of the inaccuracy there is no reason for having this variable at
all. It's just a pointless indirection and all usage sites can just use the
TICK_NSEC constant.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201117132006.766643526@linutronix.de
2020-11-19 10:48:29 +01:00
Yunfeng Ye
896b969e67 tick/sched: Release seqcount before invoking calc_load_global()
calc_load_global() does not need the sequence count protection.

[ tglx: Split it up properly and added comments ]

Signed-off-by: Yunfeng Ye <yeyunfeng@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201117132006.660902274@linutronix.de
2020-11-19 10:48:29 +01:00
Thomas Gleixner
7a35bf2a6a tick/sched: Optimize tick_do_update_jiffies64() further
Now that it's clear that there is always one tick to account, simplify the
calculations some more.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201117132006.565663056@linutronix.de
2020-11-19 10:48:29 +01:00
Yunfeng Ye
94ad2e3ced tick/sched: Reduce seqcount held scope in tick_do_update_jiffies64()
If jiffies are up to date already (caller lost the race against another
CPU) there is no point to change the sequence count. Doing that just forces
other CPUs into the seqcount retry loop in tick_nohz_next_event() for
nothing.

Just bail out early.

[ tglx: Rewrote most of it ]

Signed-off-by: Yunfeng Ye <yeyunfeng@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201117132006.462195901@linutronix.de
2020-11-19 10:48:29 +01:00
Thomas Gleixner
372acbbaa8 tick/sched: Use tick_next_period for lockless quick check
No point in doing calculations.

   tick_next_period = last_jiffies_update + tick_period

Just check whether now is before tick_next_period to figure out whether
jiffies need an update.

Add a comment why the intentional data race in the quick check is safe or
not so safe in a 32bit corner case and why we don't worry about it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201117132006.337366695@linutronix.de
2020-11-19 10:48:29 +01:00
Thomas Gleixner
c398960cd8 tick: Document protections for tick related data
The protection rules for tick_next_period and last_jiffies_update are blury
at best. Clarify this.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201117132006.197713794@linutronix.de
2020-11-19 10:48:28 +01:00
Thomas Gleixner
f73f64d568 tick/broadcast: Serialize access to tick_next_period
tick_broadcast_setup_oneshot() accesses tick_next_period twice without any
serialization. This is wrong in two aspects:

  - Reading it twice might make the broadcast data inconsistent if the
    variable is updated concurrently.

  - On 32bit systems the access might see an partial update

Protect it with jiffies_lock. That's safe as none of the callchains leading
up to this function can create a lock ordering violation:

timer interrupt
  run_local_timers()
    hrtimer_run_queues()
      hrtimer_switch_to_hres()
        tick_init_highres()
	  tick_switch_to_oneshot()
	    tick_broadcast_switch_to_oneshot()
or
     tick_check_oneshot_change()
       tick_nohz_switch_to_nohz()
         tick_switch_to_oneshot()
           tick_broadcast_switch_to_oneshot()

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201117132006.061341507@linutronix.de
2020-11-19 10:48:28 +01:00
Dmitrii Banshchikov
d055126180 bpf: Add bpf_ktime_get_coarse_ns helper
The helper uses CLOCK_MONOTONIC_COARSE source of time that is less
accurate but more performant.

We have a BPF CGROUP_SKB firewall that supports event logging through
bpf_perf_event_output(). Each event has a timestamp and currently we use
bpf_ktime_get_ns() for it. Use of bpf_ktime_get_coarse_ns() saves ~15-20
ns in time required for event logging.

bpf_ktime_get_ns():
EgressLogByRemoteEndpoint                              113.82ns    8.79M

bpf_ktime_get_coarse_ns():
EgressLogByRemoteEndpoint                               95.40ns   10.48M

Signed-off-by: Dmitrii Banshchikov <me@ubique.spb.ru>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20201117184549.257280-1-me@ubique.spb.ru
2020-11-18 23:25:32 +01:00
Hui Su
5c62634fc6 namespace: make timens_on_fork() return nothing
timens_on_fork() always return 0, and maybe not
need to judge the return value in copy_namespaces().

So make timens_on_fork() return nothing and do not
judge its return val in copy_namespaces().

Signed-off-by: Hui Su <sh_def@163.com>
Link: https://lore.kernel.org/r/20201117161750.GA45121@rlk
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2020-11-18 11:06:47 +01:00
Christoph Hellwig
16fee29b07
dma-mapping: remove the dma_direct_set_offset export
Drop the dma_direct_set_offset export and move the declaration to
dma-map-ops.h now that the Allwinner drivers have stopped calling it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
2020-11-18 09:11:38 +01:00
KP Singh
3f6719c7b6 bpf: Add bpf_bprm_opts_set helper
The helper allows modification of certain bits on the linux_binprm
struct starting with the secureexec bit which can be updated using the
BPF_F_BPRM_SECUREEXEC flag.

secureexec can be set by the LSM for privilege gaining executions to set
the AT_SECURE auxv for glibc.  When set, the dynamic linker disables the
use of certain environment variables (like LD_PRELOAD).

Signed-off-by: KP Singh <kpsingh@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20201117232929.2156341-1-kpsingh@chromium.org
2020-11-18 01:36:27 +01:00
Mickaël Salaün
fb14528e44 seccomp: Set PF_SUPERPRIV when checking capability
Replace the use of security_capable(current_cred(), ...) with
ns_capable_noaudit() which set PF_SUPERPRIV.

Since commit 98f368e9e263 ("kernel: Add noaudit variant of
ns_capable()"), a new ns_capable_noaudit() helper is available.  Let's
use it!

Cc: Jann Horn <jannh@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Tyler Hicks <tyhicks@linux.microsoft.com>
Cc: Will Drewry <wad@chromium.org>
Cc: stable@vger.kernel.org
Fixes: e2cfabdfd075 ("seccomp: add system call filtering using BPF")
Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com>
Reviewed-by: Jann Horn <jannh@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20201030123849.770769-3-mic@digikod.net
2020-11-17 12:53:22 -08:00
Mickaël Salaün
cf23705244 ptrace: Set PF_SUPERPRIV when checking capability
Commit 69f594a38967 ("ptrace: do not audit capability check when outputing
/proc/pid/stat") replaced the use of ns_capable() with
has_ns_capability{,_noaudit}() which doesn't set PF_SUPERPRIV.

Commit 6b3ad6649a4c ("ptrace: reintroduce usage of subjective credentials in
ptrace_has_cap()") replaced has_ns_capability{,_noaudit}() with
security_capable(), which doesn't set PF_SUPERPRIV neither.

Since commit 98f368e9e263 ("kernel: Add noaudit variant of ns_capable()"), a
new ns_capable_noaudit() helper is available.  Let's use it!

As a result, the signature of ptrace_has_cap() is restored to its original one.

Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Eric Paris <eparis@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Serge E. Hallyn <serge@hallyn.com>
Cc: Tyler Hicks <tyhicks@linux.microsoft.com>
Cc: stable@vger.kernel.org
Fixes: 6b3ad6649a4c ("ptrace: reintroduce usage of subjective credentials in ptrace_has_cap()")
Fixes: 69f594a38967 ("ptrace: do not audit capability check when outputing /proc/pid/stat")
Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com>
Reviewed-by: Jann Horn <jannh@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20201030123849.770769-2-mic@digikod.net
2020-11-17 12:53:22 -08:00
Christoph Hellwig
172292be01 dma-mapping: remove dma_virt_ops
Now that the RDMA core deals with devices that only do DMA mapping in
lower layers properly, there is no user for dma_virt_ops and it can be
removed.

Link: https://lore.kernel.org/r/20201106181941.1878556-11-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2020-11-17 15:22:07 -04:00
Linus Torvalds
9dacf44c38 Merge branch 'urgent-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu
Pull RCU fix from Paul McKenney:
 "A single commit that fixes a bug that was introduced a couple of merge
  windows ago, but which rather more recently converged to an
  agreed-upon fix. The bug is that interrupts can be incorrectly enabled
  while holding an irq-disabled spinlock. This can of course result in
  self-deadlocks.

  The bug is a bit difficult to trigger. It requires that a preempted
  task be blocking a preemptible-RCU grace period long enough to trigger
  an RCU CPU stall warning. In addition, an interrupt must occur at just
  the right time, and that interrupt's handler must acquire that same
  irq-disabled spinlock. Still, a deadlock is a deadlock.

  Furthermore, we do now have a fix, and that fix survives kernel test
  robot, -next, and rcutorture testing. It has also been verified by
  Sebastian as fixing the bug. Therefore..."

* 'urgent-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu:
  rcu: Don't invoke try_invoke_on_locked_down_task() with irqs disabled
2020-11-17 10:31:56 -08:00
Andy Shevchenko
5df38ca6af resource: Add test cases for new resource API
Add test cases for newly added resource APIs.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2020-11-17 18:06:28 +01:00
Andy Shevchenko
66f4fa32eb resource: Simplify region_intersects() by reducing conditionals
Now we have for 'other' and 'type' variables

other	type	return
  0	  0	REGION_DISJOINT
  0	  x	REGION_INTERSECTS
  x	  0	REGION_DISJOINT
  x	  x	REGION_MIXED

Obviously it's easier to check 'type' for 0 first instead of
currently checked 'other'.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Tested-by: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2020-11-17 18:06:28 +01:00
Boqun Feng
43be4388e9 lockdep: Put graph lock/unlock under lock_recursion protection
A warning was hit when running xfstests/generic/068 in a Hyper-V guest:

[...] ------------[ cut here ]------------
[...] DEBUG_LOCKS_WARN_ON(lockdep_hardirqs_enabled())
[...] WARNING: CPU: 2 PID: 1350 at kernel/locking/lockdep.c:5280 check_flags.part.0+0x165/0x170
[...] ...
[...] Workqueue: events pwq_unbound_release_workfn
[...] RIP: 0010:check_flags.part.0+0x165/0x170
[...] ...
[...] Call Trace:
[...]  lock_is_held_type+0x72/0x150
[...]  ? lock_acquire+0x16e/0x4a0
[...]  rcu_read_lock_sched_held+0x3f/0x80
[...]  __send_ipi_one+0x14d/0x1b0
[...]  hv_send_ipi+0x12/0x30
[...]  __pv_queued_spin_unlock_slowpath+0xd1/0x110
[...]  __raw_callee_save___pv_queued_spin_unlock_slowpath+0x11/0x20
[...]  .slowpath+0x9/0xe
[...]  lockdep_unregister_key+0x128/0x180
[...]  pwq_unbound_release_workfn+0xbb/0xf0
[...]  process_one_work+0x227/0x5c0
[...]  worker_thread+0x55/0x3c0
[...]  ? process_one_work+0x5c0/0x5c0
[...]  kthread+0x153/0x170
[...]  ? __kthread_bind_mask+0x60/0x60
[...]  ret_from_fork+0x1f/0x30

The cause of the problem is we have call chain lockdep_unregister_key()
-> <irq disabled by raw_local_irq_save()> lockdep_unlock() ->
arch_spin_unlock() -> __pv_queued_spin_unlock_slowpath() -> pv_kick() ->
__send_ipi_one() -> trace_hyperv_send_ipi_one().

Although this particular warning is triggered because Hyper-V has a
trace point in ipi sending, but in general arch_spin_unlock() may call
another function having a trace point in it, so put the arch_spin_lock()
and arch_spin_unlock() after lock_recursion protection to fix this
problem and avoid similiar problems.

Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20201113110512.1056501-1-boqun.feng@gmail.com
2020-11-17 13:15:35 +01:00
Juri Lelli
2279f540ea sched/deadline: Fix priority inheritance with multiple scheduling classes
Glenn reported that "an application [he developed produces] a BUG in
deadline.c when a SCHED_DEADLINE task contends with CFS tasks on nested
PTHREAD_PRIO_INHERIT mutexes.  I believe the bug is triggered when a CFS
task that was boosted by a SCHED_DEADLINE task boosts another CFS task
(nested priority inheritance).

 ------------[ cut here ]------------
 kernel BUG at kernel/sched/deadline.c:1462!
 invalid opcode: 0000 [#1] PREEMPT SMP
 CPU: 12 PID: 19171 Comm: dl_boost_bug Tainted: ...
 Hardware name: ...
 RIP: 0010:enqueue_task_dl+0x335/0x910
 Code: ...
 RSP: 0018:ffffc9000c2bbc68 EFLAGS: 00010002
 RAX: 0000000000000009 RBX: ffff888c0af94c00 RCX: ffffffff81e12500
 RDX: 000000000000002e RSI: ffff888c0af94c00 RDI: ffff888c10b22600
 RBP: ffffc9000c2bbd08 R08: 0000000000000009 R09: 0000000000000078
 R10: ffffffff81e12440 R11: ffffffff81e1236c R12: ffff888bc8932600
 R13: ffff888c0af94eb8 R14: ffff888c10b22600 R15: ffff888bc8932600
 FS:  00007fa58ac55700(0000) GS:ffff888c10b00000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 00007fa58b523230 CR3: 0000000bf44ab003 CR4: 00000000007606e0
 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
 PKRU: 55555554
 Call Trace:
  ? intel_pstate_update_util_hwp+0x13/0x170
  rt_mutex_setprio+0x1cc/0x4b0
  task_blocks_on_rt_mutex+0x225/0x260
  rt_spin_lock_slowlock_locked+0xab/0x2d0
  rt_spin_lock_slowlock+0x50/0x80
  hrtimer_grab_expiry_lock+0x20/0x30
  hrtimer_cancel+0x13/0x30
  do_nanosleep+0xa0/0x150
  hrtimer_nanosleep+0xe1/0x230
  ? __hrtimer_init_sleeper+0x60/0x60
  __x64_sys_nanosleep+0x8d/0xa0
  do_syscall_64+0x4a/0x100
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
 RIP: 0033:0x7fa58b52330d
 ...
 ---[ end trace 0000000000000002 ]—

He also provided a simple reproducer creating the situation below:

 So the execution order of locking steps are the following
 (N1 and N2 are non-deadline tasks. D1 is a deadline task. M1 and M2
 are mutexes that are enabled * with priority inheritance.)

 Time moves forward as this timeline goes down:

 N1              N2               D1
 |               |                |
 |               |                |
 Lock(M1)        |                |
 |               |                |
 |             Lock(M2)           |
 |               |                |
 |               |              Lock(M2)
 |               |                |
 |             Lock(M1)           |
 |             (!!bug triggered!) |

Daniel reported a similar situation as well, by just letting ksoftirqd
run with DEADLINE (and eventually block on a mutex).

Problem is that boosted entities (Priority Inheritance) use static
DEADLINE parameters of the top priority waiter. However, there might be
cases where top waiter could be a non-DEADLINE entity that is currently
boosted by a DEADLINE entity from a different lock chain (i.e., nested
priority chains involving entities of non-DEADLINE classes). In this
case, top waiter static DEADLINE parameters could be null (initialized
to 0 at fork()) and replenish_dl_entity() would hit a BUG().

Fix this by keeping track of the original donor and using its parameters
when a task is boosted.

Reported-by: Glenn Elliott <glenn@aurora.tech>
Reported-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Link: https://lkml.kernel.org/r/20201117061432.517340-1-juri.lelli@redhat.com
2020-11-17 13:15:28 +01:00
Peter Zijlstra
ec618b84f6 sched: Fix rq->nr_iowait ordering
schedule()				ttwu()
    deactivate_task();			  if (p->on_rq && ...) // false
					    atomic_dec(&task_rq(p)->nr_iowait);
    if (prev->in_iowait)
      atomic_inc(&rq->nr_iowait);

Allows nr_iowait to be decremented before it gets incremented,
resulting in more dodgy IO-wait numbers than usual.

Note that because we can now do ttwu_queue_wakelist() before
p->on_cpu==0, we lose the natural ordering and have to further delay
the decrement.

Fixes: c6e7bd7afaeb ("sched/core: Optimize ttwu() spinning on p->on_cpu")
Reported-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Link: https://lkml.kernel.org/r/20201117093829.GD3121429@hirez.programming.kicks-ass.net
2020-11-17 13:15:28 +01:00
Quentin Perret
8e1ac4299a sched/fair: Fix overutilized update in enqueue_task_fair()
enqueue_task_fair() attempts to skip the overutilized update for new
tasks as their util_avg is not accurate yet. However, the flag we check
to do so is overwritten earlier on in the function, which makes the
condition pretty much a nop.

Fix this by saving the flag early on.

Fixes: 2802bf3cd936 ("sched/fair: Add over-utilization/tipping point indicator")
Reported-by: Rick Yiu <rickyiu@google.com>
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20201112111201.2081902-1-qperret@google.com
2020-11-17 13:15:27 +01:00
Gabriel Krisman Bertazi
2991552447 entry: Drop usage of TIF flags in the generic syscall code
Now that the flags migration in the common syscall entry code is complete
and the code relies exclusively on thread_info::syscall_work, clean up the
accesses to TI flags in that path.

Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20201116174206.2639648-10-krisman@collabora.com
2020-11-16 21:53:16 +01:00
Gabriel Krisman Bertazi
785dc4eb7f audit: Migrate to use SYSCALL_WORK flag
On architectures using the generic syscall entry code the architecture
independent syscall work is moved to flags in thread_info::syscall_work.
This removes architecture dependencies and frees up TIF bits.

Define SYSCALL_WORK_SYSCALL_AUDIT, use it in the generic entry code and
convert the code which uses the TIF specific helper functions to use the
new *_syscall_work() helpers which either resolve to the new mode for users
of the generic entry code or to the TIF based functions for the other
architectures.

Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20201116174206.2639648-9-krisman@collabora.com
2020-11-16 21:53:16 +01:00
Gabriel Krisman Bertazi
64eb35f701 ptrace: Migrate TIF_SYSCALL_EMU to use SYSCALL_WORK flag
On architectures using the generic syscall entry code the architecture
independent syscall work is moved to flags in thread_info::syscall_work.
This removes architecture dependencies and frees up TIF bits.

Define SYSCALL_WORK_SYSCALL_EMU, use it in the generic entry code and
convert the code which uses the TIF specific helper functions to use the
new *_syscall_work() helpers which either resolve to the new mode for users
of the generic entry code or to the TIF based functions for the other
architectures.

Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20201116174206.2639648-8-krisman@collabora.com
2020-11-16 21:53:16 +01:00
Gabriel Krisman Bertazi
64c19ba29b ptrace: Migrate to use SYSCALL_TRACE flag
On architectures using the generic syscall entry code the architecture
independent syscall work is moved to flags in thread_info::syscall_work.
This removes architecture dependencies and frees up TIF bits.

Define SYSCALL_WORK_SYSCALL_TRACE, use it in the generic entry code and
convert the code which uses the TIF specific helper functions to use the
new *_syscall_work() helpers which either resolve to the new mode for users
of the generic entry code or to the TIF based functions for the other
architectures.

Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20201116174206.2639648-7-krisman@collabora.com
2020-11-16 21:53:16 +01:00
Gabriel Krisman Bertazi
524666cb5d tracepoints: Migrate to use SYSCALL_WORK flag
On architectures using the generic syscall entry code the architecture
independent syscall work is moved to flags in thread_info::syscall_work.
This removes architecture dependencies and frees up TIF bits.

Define SYSCALL_WORK_SYSCALL_TRACEPOINT, use it in the generic entry code
and convert the code which uses the TIF specific helper functions to use
the new *_syscall_work() helpers which either resolve to the new mode for
users of the generic entry code or to the TIF based functions for the other
architectures.

Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20201116174206.2639648-6-krisman@collabora.com
2020-11-16 21:53:15 +01:00