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Currently root_task_group.shares and cfs_bandwidth are initialized for
each online cpu, which not necessary.
Let's take it out to do it only once.
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200423214443.29994-1-richard.weiyang@gmail.com
The code is executed with preemption(and interrupts) disabled,
so it's safe to use __this_cpu_write().
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200421144123.33580-1-songmuchun@bytedance.com
In the CPU-offline process, it calls mmdrop() after idle entry and the
subsequent call to cpuhp_report_idle_dead(). Once execution passes the
call to rcu_report_dead(), RCU is ignoring the CPU, which results in
lockdep complaining when mmdrop() uses RCU from either memcg or
debugobjects below.
Fix it by cleaning up the active_mm state from BP instead. Every arch
which has CONFIG_HOTPLUG_CPU should have already called idle_task_exit()
from AP. The only exception is parisc because it switches them to
&init_mm unconditionally (see smp_boot_one_cpu() and smp_cpu_init()),
but the patch will still work there because it calls mmgrab(&init_mm) in
smp_cpu_init() and then should call mmdrop(&init_mm) in finish_cpu().
WARNING: suspicious RCU usage
-----------------------------
kernel/workqueue.c:710 RCU or wq_pool_mutex should be held!
other info that might help us debug this:
RCU used illegally from offline CPU!
Call Trace:
dump_stack+0xf4/0x164 (unreliable)
lockdep_rcu_suspicious+0x140/0x164
get_work_pool+0x110/0x150
__queue_work+0x1bc/0xca0
queue_work_on+0x114/0x120
css_release+0x9c/0xc0
percpu_ref_put_many+0x204/0x230
free_pcp_prepare+0x264/0x570
free_unref_page+0x38/0xf0
__mmdrop+0x21c/0x2c0
idle_task_exit+0x170/0x1b0
pnv_smp_cpu_kill_self+0x38/0x2e0
cpu_die+0x48/0x64
arch_cpu_idle_dead+0x30/0x50
do_idle+0x2f4/0x470
cpu_startup_entry+0x38/0x40
start_secondary+0x7a8/0xa80
start_secondary_resume+0x10/0x14
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Qian Cai <cai@lca.pw>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Link: https://lkml.kernel.org/r/20200401214033.8448-1-cai@lca.pw
Function sched_init_granularity() is only called from __init
functions, so mark it __init as well.
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Link: https://lkml.kernel.org/r/20200406074750.56533-1-songmuchun@bytedance.com
In order to prevent possible hardlockup of sched_cfs_period_timer()
loop, loop count is introduced to denote whether to scale quota and
period or not. However, scale is done between forwarding period timer
and refilling cfs bandwidth runtime, which means that period timer is
forwarded with old "period" while runtime is refilled with scaled
"quota".
Move do_sched_cfs_period_timer() before scaling to solve this.
Fixes: 2e8e19226398 ("sched/fair: Limit sched_cfs_period_timer() loop to avoid hard lockup")
Signed-off-by: Huaixin Chang <changhuaixin@linux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Ben Segall <bsegall@google.com>
Reviewed-by: Phil Auld <pauld@redhat.com>
Link: https://lkml.kernel.org/r/20200420024421.22442-3-changhuaixin@linux.alibaba.com
Introduce a new function put_prev_task_balance() to do the balance
when necessary, and then put previous task back to the run queue.
This function is extracted from pick_next_task() to prepare for
future usage by other type of task picking logic.
No functional change.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Link: https://lkml.kernel.org/r/5a99860cf66293db58a397d6248bcb2eee326776.1587464698.git.yu.c.chen@intel.com
After Commit 6e2df0581f56 ("sched: Fix pick_next_task() vs 'change'
pattern race"), there is no need to expose newidle_balance() as it
is only used within fair.c file. Change this function back to static again.
No functional change.
Reported-by: kbuild test robot <lkp@intel.com>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/83cd3030b031ca5d646cd5e225be10e7a0fdd8f5.1587464698.git.yu.c.chen@intel.com
That flag is set unconditionally in sd_init(), and no one checks for it
anymore. Remove it.
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200415210512.805-5-valentin.schneider@arm.com
The SD_LOAD_BALANCE flag is set unconditionally for all domains in
sd_init(). By making the sched_domain->flags syctl interface read-only, we
have removed the last piece of code that could clear that flag - as such,
it will now be always present. Rather than to keep carrying it along, we
can work towards getting rid of it entirely.
cpusets don't need it because they can make CPUs be attached to the NULL
domain (e.g. cpuset with sched_load_balance=0), or to a partitioned
root_domain, i.e. a sched_domain hierarchy that doesn't span the entire
system (e.g. root cpuset with sched_load_balance=0 and sibling cpusets with
sched_load_balance=1).
isolcpus apply the same "trick": isolated CPUs are explicitly taken out of
the sched_domain rebuild (using housekeeping_cpumask()), so they get the
NULL domain treatment as well.
Remove the checks against SD_LOAD_BALANCE.
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200415210512.805-4-valentin.schneider@arm.com
Writing to the sysctl of a sched_domain->flags directly updates the value of
the field, and goes nowhere near update_top_cache_domain(). This means that
the cached domain pointers can end up containing stale data (e.g. the
domain pointed to doesn't have the relevant flag set anymore).
Explicit domain walks that check for flags will be affected by
the write, but this won't be in sync with the cached pointers which will
still point to the domains that were cached at the last sched_domain
build.
In other words, writing to this interface is playing a dangerous game. It
could be made to trigger an update of the cached sched_domain pointers when
written to, but this does not seem to be worth the trouble. Make it
read-only.
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200415210512.805-3-valentin.schneider@arm.com
The last use of that parameter was removed by commit
57abff067a08 ("sched/fair: Rework find_idlest_group()")
Get rid of the parameter.
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20200415210512.805-2-valentin.schneider@arm.com
With CONFIG_DEBUG_ATOMIC_SLEEP=y and CONFIG_CGROUPS=y, kernel oopses in
non-preemptible context look untidy; after the main oops, the kernel prints
a "sleeping function called from invalid context" report because
exit_signals() -> cgroup_threadgroup_change_begin() -> percpu_down_read()
can sleep, and that happens before the preempt_count_set(PREEMPT_ENABLED)
fixup.
It looks like the same thing applies to profile_task_exit() and
kcov_task_exit().
Fix it by moving the preemption fixup up and the calls to
profile_task_exit() and kcov_task_exit() down.
Fixes: 1dc0fffc48af ("sched/core: Robustify preemption leak checks")
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200305220657.46800-1-jannh@google.com
We only consider group_balance_cpu() after there is no idle
cpu. So, just do comparison before return at these two cases.
Signed-off-by: Peng Wang <rocking@linux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/245c792f0e580b3ca342ad61257f4c066ee0f84f.1586594833.git.rocking@linux.alibaba.com
This is mostly a revert of commit:
baa9be4ffb55 ("sched/fair: Fix throttle_list starvation with low CFS quota")
The primary use of distribute_running was to determine whether to add
throttled entities to the head or the tail of the throttled list. Now
that we always add to the tail, we can remove this field.
The other use of distribute_running is in the slack_timer, so that we
don't start a distribution while one is already running. However, even
in the event that this race occurs, it is fine to have two distributions
running (especially now that distribute grabs the cfs_b->lock to
determine remaining quota before assigning).
Signed-off-by: Josh Don <joshdon@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Phil Auld <pauld@redhat.com>
Tested-by: Phil Auld <pauld@redhat.com>
Link: https://lkml.kernel.org/r/20200410225208.109717-3-joshdon@google.com
There is a race window in which an entity begins throttling before quota
is added to the pool, but does not finish throttling until after we have
finished with distribute_cfs_runtime(). This entity is not observed by
distribute_cfs_runtime() because it was not on the throttled list at the
time that distribution was running. This race manifests as rare
period-length statlls for such entities.
Rather than heavy-weight the synchronization with the progress of
distribution, we can fix this by aborting throttling if bandwidth has
become available. Otherwise, we immediately add the entity to the
throttled list so that it can be observed by a subsequent distribution.
Additionally, we can remove the case of adding the throttled entity to
the head of the throttled list, and simply always add to the tail.
Thanks to 26a8b12747c97, distribute_cfs_runtime() no longer holds onto
its own pool of runtime. This means that if we do hit the !assign and
distribute_running case, we know that distribution is about to end.
Signed-off-by: Paul Turner <pjt@google.com>
Signed-off-by: Ben Segall <bsegall@google.com>
Signed-off-by: Josh Don <joshdon@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Phil Auld <pauld@redhat.com>
Link: https://lkml.kernel.org/r/20200410225208.109717-2-joshdon@google.com
Under rare circumstances, task_function_call() can repeatedly fail and
cause a soft lockup.
There is a slight race where the process is no longer running on the cpu
we targeted by the time remote_function() runs. The code will simply
try again. If we are very unlucky, this will continue to fail, until a
watchdog fires. This can happen in a heavily loaded, multi-core virtual
machine.
Reported-by: syzbot+bb4935a5c09b5ff79940@syzkaller.appspotmail.com
Signed-off-by: Barret Rhoden <brho@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200414222920.121401-1-brho@google.com
Fix to return negative error code -EFAULT from the copy_to_user() error
handling case instead of 0, as done elsewhere in this function.
Fixes: bd513cd08f10 ("bpf: add MAP_LOOKUP_AND_DELETE_ELEM syscall")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200430081851.166996-1-weiyongjun1@huawei.com
The current posix-cpu-timer code uses pids when holding persistent
references in timers. However the lookups from clock_id_t still return
tasks that need to be converted into pids for use.
This results in usage being pid->task->pid and that can race with
release_task and de_thread. This can lead to some not wrong but
surprising results. Surprising enough that Oleg and I both thought
there were some bugs in the code for a while.
This set of changes modifies the code to just lookup, verify, and return
pids from the clockid_t lookups to remove those potentialy troublesome
races.
Eric W. Biederman (3):
posix-cpu-timers: Extend rcu_read_lock removing task_struct references
posix-cpu-timers: Replace cpu_timer_pid_type with clock_pid_type
posix-cpu-timers: Replace __get_task_for_clock with pid_for_clock
kernel/time/posix-cpu-timers.c | 102 ++++++++++++++++++-----------------------
1 file changed, 45 insertions(+), 57 deletions(-)
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Starting from 2c4704756cab ("pids: Move the pgrp and session pid pointers
from task_struct to signal_struct") __task_pid_nr_ns() doesn't dereference
task->group_leader, we can remove the pid_alive() check.
pid_nr_ns() has to check pid != NULL anyway, pid_alive() just adds the
unnecessary confusion.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Removing the pcrypt module triggers this:
general protection fault, probably for non-canonical
address 0xdead000000000122
CPU: 5 PID: 264 Comm: modprobe Not tainted 5.6.0+ #2
Hardware name: QEMU Standard PC
RIP: 0010:__cpuhp_state_remove_instance+0xcc/0x120
Call Trace:
padata_sysfs_release+0x74/0xce
kobject_put+0x81/0xd0
padata_free+0x12/0x20
pcrypt_exit+0x43/0x8ee [pcrypt]
padata instances wrongly use the same hlist node for the online and dead
states, so __padata_free()'s second cpuhp remove call chokes on the node
that the first poisoned.
cpuhp multi-instance callbacks only walk forward in cpuhp_step->list and
the same node is linked in both the online and dead lists, so the list
corruption that results from padata_alloc() adding the node to a second
list without removing it from the first doesn't cause problems as long
as no instances are freed.
Avoid the issue by giving each state its own node.
Fixes: 894c9ef9780c ("padata: validate cpumask without removed CPU during offline")
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: linux-crypto@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: stable@vger.kernel.org # v5.4+
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Hiding the only using of bpf_link_type_strs[] in an #ifdef causes
an unused-variable warning:
kernel/bpf/syscall.c:2280:20: error: 'bpf_link_type_strs' defined but not used [-Werror=unused-variable]
2280 | static const char *bpf_link_type_strs[] = {
Move the definition into the same #ifdef.
Fixes: f2e10bff16a0 ("bpf: Add support for BPF_OBJ_GET_INFO_BY_FD for bpf_link")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200429132217.1294289-1-arnd@arndb.de
White-list map lookup for SOCKMAP/SOCKHASH from BPF. Lookup returns a
pointer to a full socket and acquires a reference if necessary.
To support it we need to extend the verifier to know that:
(1) register storing the lookup result holds a pointer to socket, if
lookup was done on SOCKMAP/SOCKHASH, and that
(2) map lookup on SOCKMAP/SOCKHASH is a reference acquiring operation,
which needs a corresponding reference release with bpf_sk_release.
On sock_map side, lookup handlers exposed via bpf_map_ops now bump
sk_refcnt if socket is reference counted. In turn, bpf_sk_select_reuseport,
the only in-kernel user of SOCKMAP/SOCKHASH ops->map_lookup_elem, was
updated to release the reference.
Sockets fetched from a map can be used in the same way as ones returned by
BPF socket lookup helpers, such as bpf_sk_lookup_tcp. In particular, they
can be used with bpf_sk_assign to direct packets toward a socket on TC
ingress path.
Suggested-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200429181154.479310-2-jakub@cloudflare.com
Now that the codes store references to pids instead of referendes to
tasks. Looking up a task for a clock instead of looking up a struct
pid makes the code more difficult to verify it is correct than
necessary.
In posix_cpu_timers_create get_task_pid can race with release_task for
threads and return a NULL pid. As put_pid and cpu_timer_task_rcu
handle NULL pids just fine the code works without problems but it is
an extra case to consider and keep in mind while verifying and
modifying the code.
There are races with de_thread to consider that only don't apply
because thread clocks are only allowed for threads in the same
thread_group.
So instead of leaving a burden for people making modification to the
code in the future return a rcu protected struct pid for the clock
instead.
The logic for __get_task_for_pid and lookup_task has been folded into
the new function pid_for_clock with the only change being the logic
has been modified from working on a task to working on a pid that
will be returned.
In posix_cpu_clock_get instead of calling pid_for_clock checking the
result and then calling pid_task to get the task. The result of
pid_for_clock is fed directly into pid_task. This is safe because
pid_task handles NULL pids. As such an extra error check was
unnecessary.
Instead of hiding the flag that enables the special clock_gettime
handling, I have made the 3 callers just pass the flag in themselves.
That is less code and seems just as simple to work with as the
wrapper functions.
Historically the clock_gettime special case of allowing a process
clock to be found by the thread id did not even exist [33ab0fec3352]
but Thomas Gleixner reports that he has found code that uses that
functionality [55e8c8eb2c7b].
Link: https://lkml.kernel.org/r/87zhaxqkwa.fsf@nanos.tec.linutronix.de/
Ref: 33ab0fec3352 ("posix-timers: Consolidate posix_cpu_clock_get()")
Ref: 55e8c8eb2c7b ("posix-cpu-timers: Store a reference to a pid not a task")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Taking a clock and returning a pid_type is a more general and
a superset of taking a timer and returning a pid_type.
Perform this generalization so that future changes may use
this code on clocks as well as timers.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Now that the code stores of pid references it is no longer necessary
or desirable to take a reference on task_struct in __get_task_for_clock.
Instead extend the scope of rcu_read_lock and remove the reference
counting on struct task_struct entirely.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Add ability to fetch bpf_link details through BPF_OBJ_GET_INFO_BY_FD command.
Also enhance show_fdinfo to potentially include bpf_link type-specific
information (similarly to obj_info).
Also introduce enum bpf_link_type stored in bpf_link itself and expose it in
UAPI. bpf_link_tracing also now will store and return bpf_attach_type.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200429001614.1544-5-andriin@fb.com
Add support to look up bpf_link by ID and iterate over all existing bpf_links
in the system. GET_FD_BY_ID code handles not-yet-ready bpf_link by checking
that its ID hasn't been set to non-zero value yet. Setting bpf_link's ID is
done as the very last step in finalizing bpf_link, together with installing
FD. This approach allows users of bpf_link in kernel code to not worry about
races between user-space and kernel code that hasn't finished attaching and
initializing bpf_link.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200429001614.1544-4-andriin@fb.com
Generate ID for each bpf_link using IDR, similarly to bpf_map and bpf_prog.
bpf_link creation, initialization, attachment, and exposing to user-space
through FD and ID is a complicated multi-step process, abstract it away
through bpf_link_primer and bpf_link_prime(), bpf_link_settle(), and
bpf_link_cleanup() internal API. They guarantee that until bpf_link is
properly attached, user-space won't be able to access partially-initialized
bpf_link either from FD or ID. All this allows to simplify bpf_link attachment
and error handling code.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200429001614.1544-3-andriin@fb.com
Make bpf_link update support more generic by making it into another
bpf_link_ops methods. This allows generic syscall handling code to be agnostic
to various conditionally compiled features (e.g., the case of
CONFIG_CGROUP_BPF). This also allows to keep link type-specific code to remain
static within respective code base. Refactor existing bpf_cgroup_link code and
take advantage of this.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200429001614.1544-2-andriin@fb.com
Audit the action of unregistering ebtables and x_tables.
See: https://github.com/linux-audit/audit-kernel/issues/44
Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
NETFILTER_CFG record generation was inconsistent for x_tables and
ebtables configuration changes. The call was needlessly messy and there
were supporting records missing at times while they were produced when
not requested. Simplify the logging call into a new audit_log_nfcfg
call. Honour the audit_enabled setting while more consistently
recording information including supporting records by tidying up dummy
checks.
Add an op= field that indicates the operation being performed (register
or replace).
Here is the enhanced sample record:
type=NETFILTER_CFG msg=audit(1580905834.919:82970): table=filter family=2 entries=83 op=replace
Generate audit NETFILTER_CFG records on ebtables table registration.
Previously this was being done for x_tables registration and replacement
operations and ebtables table replacement only.
See: https://github.com/linux-audit/audit-kernel/issues/25
See: https://github.com/linux-audit/audit-kernel/issues/35
See: https://github.com/linux-audit/audit-kernel/issues/43
Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Now that both !thread paths through lookup_task call
thread_group_leader, unify them into the single test at the end of
lookup_task.
This unification just makes it clear what is happening in the gettime
special case of lookup_task.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Replace has_group_leader_pid with thread_group_leader. Years ago Oleg
suggested changing thread_group_leader to has_group_leader_pid to handle
races. Looking at the code then and now I don't see how it ever helped.
Especially as then the code really did need to be the
thread_group_leader.
Today it doesn't make a difference if thread_group_leader races with
de_thread as the task returned from lookup_task in the non-thread case is
just used to find values in task->signal.
Since the races with de_thread have never been handled revert
has_group_header_pid to thread_group_leader for clarity.
Update the comment in lookup_task to remove implementation details that
are no longer true and to mention task->signal instead of task->sighand,
as the relevant cpu timer details are all in task->signal.
Ref: 55e8c8eb2c7b ("posix-cpu-timers: Store a reference to a pid not a task")
Ref: c0deae8c9587 ("posix-cpu-timers: Rcu_read_lock/unlock protect find_task_by_vpid call")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
When the thread group leader changes during exec and the old leaders
thread is reaped proc_flush_pid will flush the dentries for the entire
process because the leader still has it's original pid.
Fix this by exchanging the pids in an rcu safe manner,
and wrapping the code to do that up in a helper exchange_tids.
When I removed switch_exec_pids and introduced this behavior
in d73d65293e3e ("[PATCH] pidhash: kill switch_exec_pids") there
really was nothing that cared as flushing happened with
the cached dentry and de_thread flushed both of them on exec.
This lack of fully exchanging pids became a problem a few months later
when I introduced 48e6484d4902 ("[PATCH] proc: Rewrite the proc dentry
flush on exit optimization"). Which overlooked the de_thread case
was no longer swapping pids, and I was looking up proc dentries
by task->pid.
The current behavior isn't properly a bug as everything in proc will
continue to work correctly just a little bit less efficiently. Fix
this just so there are no little surprise corner cases waiting to bite
people.
-- Oleg points out this could be an issue in next_tgid in proc where
has_group_leader_pid is called, and reording some of the assignments
should fix that.
-- Oleg points out this will break the 10 year old hack in __exit_signal.c
> /*
> * This can only happen if the caller is de_thread().
> * FIXME: this is the temporary hack, we should teach
> * posix-cpu-timers to handle this case correctly.
> */
> if (unlikely(has_group_leader_pid(tsk)))
> posix_cpu_timers_exit_group(tsk);
The code in next_tgid has been changed to use PIDTYPE_TGID,
and the posix cpu timers code has been fixed so it does not
need the 10 year old hack, so this should be safe to merge
now.
Link: https://lore.kernel.org/lkml/87h7x3ajll.fsf_-_@x220.int.ebiederm.org/
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Fixes: 48e6484d4902 ("[PATCH] proc: Rewrite the proc dentry flush on exit optimization").
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Pull in Christoph Hellwig's series that changes the sysctl's ->proc_handler
methods to take kernel pointers instead. It gets rid of the set_fs address
space overrides used by BPF. As per discussion, pull in the feature branch
into bpf-next as it relates to BPF sysctl progs.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200427071508.GV23230@ZenIV.linux.org.uk/T/
Except for a few of the networking hooks called from modular ipv4
or ipv6 code, all of hooks are just called from guaranteed to be
built-in code.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrey Ignatov <rdna@fb.com>
Link: https://lore.kernel.org/bpf/20200424064338.538313-2-hch@lst.de
A spin lock is held in insert_report_filterlist(), so the krealloc()
should use GFP_ATOMIC. This commit therefore makes this change.
Reviewed-by: Marco Elver <elver@google.com>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The n_barrier_successes, n_barrier_attempts, and
n_rcu_torture_barrier_error variables are updated (without access
markings) by the main rcu_barrier() test kthread, and accessed (also
without access markings) by the rcu_torture_stats() kthread. This of
course can result in KCSAN complaints.
Because the accesses are in diagnostic prints, this commit uses
data_race() to excuse the diagnostic prints from the data race. If this
were to ever cause bogus statistics prints (for example, due to store
tearing), any misleading information would be disambiguated by the
presence or absence of an rcutorture splat.
This data race was reported by KCSAN. Not appropriate for backporting
due to failure being unlikely and due to the mild consequences of the
failure, namely a confusing rcutorture console message.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
This commit adds stubs for KCSAN's data_race(), ASSERT_EXCLUSIVE_WRITER(),
and ASSERT_EXCLUSIVE_ACCESS() macros to allow code using these macros to
move ahead.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
When all quiescent states have been seen, it is normally the grace-period
kthread that is in trouble. Although the existing stack trace from
the current CPU might possibly provide useful information, experience
indicates that there is too much noise for this to be worthwhile.
This commit therefore removes this stack trace from the output.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
If the grace-period kthread is starved, idle threads' extended quiescent
states are not reported. These idle threads thus wrongly appear to
be blocking the current grace period. This commit therefore tags such
idle threads as probable false positives when the grace-period kthread
is being starved.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Although the accesses used to determine whether or not an expedited
stall should be printed are an integral part of the concurrency algorithm
governing use of the corresponding variables, the values that are simply
printed are ancillary. As such, it is best to use data_race() for these
accesses in order to provide the greatest latitude in the use of KCSAN
for the other accesses that are an integral part of the algorithm. This
commit therefore changes the relevant uses of READ_ONCE() to data_race().
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit replaces the schedule_on_each_cpu(ftrace_sync) instances
with synchronize_rcu_tasks_rude().
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@redhat.com>
[ paulmck: Make Kconfig adjustments noted by kbuild test robot. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit allows TASKS_TRACE_RCU to be used independently of TASKS_RCU
and vice versa.
[ paulmck: Fix conditional compilation per kbuild test robot feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds a failure-return count for smp_call_function_single(),
and adds this to the console messages for rcutorture writer stalls and at
the end of rcutorture testing.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
