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As pointed out by commit
de9b8f5dcbd9 ("sched: Fix crash trying to dequeue/enqueue the idle thread")
init_idle() can and will be invoked more than once on the same idle
task. At boot time, it is invoked for the boot CPU thread by
sched_init(). Then smp_init() creates the threads for all the secondary
CPUs and invokes init_idle() on them.
As the hotplug machinery brings the secondaries to life, it will issue
calls to idle_thread_get(), which itself invokes init_idle() yet again.
In this case it's invoked twice more per secondary: at _cpu_up(), and at
bringup_cpu().
Given smp_init() already initializes the idle tasks for all *possible*
CPUs, no further initialization should be required. Now, removing
init_idle() from idle_thread_get() exposes some interesting expectations
with regards to the idle task's preempt_count: the secondary startup always
issues a preempt_disable(), requiring some reset of the preempt count to 0
between hot-unplug and hotplug, which is currently served by
idle_thread_get() -> idle_init().
Given the idle task is supposed to have preemption disabled once and never
see it re-enabled, it seems that what we actually want is to initialize its
preempt_count to PREEMPT_DISABLED and leave it there. Do that, and remove
init_idle() from idle_thread_get().
Secondary startups were patched via coccinelle:
@begone@
@@
-preempt_disable();
...
cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210512094636.2958515-1-valentin.schneider@arm.com
request_irq() is preferred over setup_irq(). Invocations of setup_irq()
occur after memory allocators are ready.
Per tglx[1], setup_irq() existed in olden days when allocators were not
ready by the time early interrupts were initialized.
Hence replace setup_irq() by request_irq().
[1] https://lkml.kernel.org/r/alpine.DEB.2.20.1710191609480.1971@nanos
Signed-off-by: afzal mohammed <afzal.mohd.ma@gmail.com>
Message-Id: <20200304004112.3848-1-afzal.mohd.ma@gmail.com>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
CONFIG_DEBUG_KERNEL should not impact code generation. Use the newly
defined CONFIG_DEBUG_MISC instead to keep the current code.
Link: http://lkml.kernel.org/r/20190413224438.10802-5-okaya@kernel.org
Signed-off-by: Sinan Kaya <okaya@kernel.org>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Max Filippov <jcmvbkbc@gmail.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: Anders Roxell <anders.roxell@linaro.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Florian Westphal <fw@strlen.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: Paul Burton <paul.burton@mips.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Thomas Bogendoerfer <tbogendoerfer@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Don't skip current CPU in send_ipi_message: callers of this function
take care of it and it's harmless anyway.
Don't clear IPI bits one by one, clear all that were read at once.
Check IPI register in a loop in case new IPI was posted while previous
was being handled.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
This fixes the following warning at boot when the kernel is booted on a
board with more CPU cores than was configured in NR_CPUS:
smp_init_cpus: Core Count = 8
smp_init_cpus: Core Id = 0
------------[ cut here ]------------
WARNING: CPU: 0 PID: 0 at include/linux/cpumask.h:121 smp_init_cpus+0x54/0x74
Modules linked in:
CPU: 0 PID: 0 Comm: swapper Not tainted 5.0.0-rc3-00015-g1459333f88a0 #124
Call Trace:
__warn$part$3+0x6a/0x7c
warn_slowpath_null+0x35/0x3c
smp_init_cpus+0x54/0x74
setup_arch+0x1c0/0x1d0
start_kernel+0x44/0x310
_startup+0x107/0x107
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
- add missing memory barriers to the secondary CPU synchronization spin
loops; add comment to the matching memory barrier in the boot_secondary
and __cpu_die functions;
- use READ_ONCE/WRITE_ONCE to access cpu_start_id/cpu_start_ccount
instead of reading/writing them directly;
- re-initialize cpu_running every time before starting secondary CPU to
flush possible previous CPU startup results.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
We are going to split <linux/sched/task_stack.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.
Create a trivial placeholder <linux/sched/task_stack.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.
Include the new header in the files that are going to need it.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
We are going to split <linux/sched/hotplug.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.
Create a trivial placeholder <linux/sched/hotplug.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.
Include the new header in the files that are going to need it.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Apart from adding the helper function itself, the rest of the kernel is
converted mechanically using:
git grep -l 'atomic_inc.*mm_users' | xargs sed -i 's/atomic_inc(&\(.*\)->mm_users);/mmget\(\1\);/'
git grep -l 'atomic_inc.*mm_users' | xargs sed -i 's/atomic_inc(&\(.*\)\.mm_users);/mmget\(\&\1\);/'
This is needed for a later patch that hooks into the helper, but might
be a worthwhile cleanup on its own.
(Michal Hocko provided most of the kerneldoc comment.)
Link: http://lkml.kernel.org/r/20161218123229.22952-2-vegard.nossum@oracle.com
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Apart from adding the helper function itself, the rest of the kernel is
converted mechanically using:
git grep -l 'atomic_inc.*mm_count' | xargs sed -i 's/atomic_inc(&\(.*\)->mm_count);/mmgrab\(\1\);/'
git grep -l 'atomic_inc.*mm_count' | xargs sed -i 's/atomic_inc(&\(.*\)\.mm_count);/mmgrab\(\&\1\);/'
This is needed for a later patch that hooks into the helper, but might
be a worthwhile cleanup on its own.
(Michal Hocko provided most of the kerneldoc comment.)
Link: http://lkml.kernel.org/r/20161218123229.22952-1-vegard.nossum@oracle.com
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Let the non boot cpus call into idle with the corresponding hotplug state, so
the hotplug core can handle the further bringup. That's a first step to
convert the boot side of the hotplugged cpus to do all the synchronization
with the other side through the state machine. For now it'll only start the
hotplug thread and kick the full bringup of the cpu.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20160226182341.614102639@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
there is a small possibility that wake_up of softirq thread
happens between local_irq_enable() and set_cpu_online(). In
this case affinity of the thread changes to fallback affinity
(i.e. CPU0). This may be a source of problems.
The patch kills that possibility.
Signed-off-by: Kirill Tkhai <tkhai@yandex.ru>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
This is largely based on SMP code from the xtensa-2.6.29-smp tree by
Piet Delaney, Marc Gauthier, Joe Taylor, Christian Zankel (and possibly
other Tensilica folks).
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Chris Zankel <chris@zankel.net>
