Messages in this thread Patch in this message | | | Date | Mon, 18 May 2015 08:45:52 +0200 | From | Ingo Molnar <> | Subject | Re: Regression: turbostat stops working after suspend/resume cycle |
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* Gabriele Mazzotta <gabriele.mzt@gmail.com> wrote:
> Hi, > > I've recently noticed that if I suspend and resume my laptop, I can no > longer execute turbostat. This is what I get when I try to start it: > # turbostat > Could not migrate to CPU 1 > turbostat: re-initialized with num_cpus 4 > Could not migrate to CPU 1 > > Since everything works as expected with v4.0, I ran a bisection and > found that commit 3c18d447b3b36a8d ("sched/core: Check for available > DL bandwidth in cpuset_cpu_inactive()") is the cause of the regression. > > I don't know if there's something else affected by that change, but > I can consistently reproduce the bug with turbostat. > > I can provide more info if needed.
Does this commit:
533445c6e533 sched/core: Fix regression in cpuset_cpu_inactive() for suspend
which is already in Linus's tree, and which should be part of -rc4, fix it? Also attached below.
Thanks,
Ingo
====================> From 533445c6e53368569e50ab3fb712230c03d523f3 Mon Sep 17 00:00:00 2001 From: Omar Sandoval <osandov@osandov.com> Date: Mon, 4 May 2015 03:09:36 -0700 Subject: [PATCH] sched/core: Fix regression in cpuset_cpu_inactive() for suspend
Commit 3c18d447b3b3 ("sched/core: Check for available DL bandwidth in cpuset_cpu_inactive()"), a SCHED_DEADLINE bugfix, had a logic error that caused a regression in setting a CPU inactive during suspend. I ran into this when a program was failing pthread_setaffinity_np() with EINVAL after a suspend+wake up.
A simple reproducer:
$ ./a.out sched_setaffinity: Success $ systemctl suspend $ ./a.out sched_setaffinity: Invalid argument
... where ./a.out is:
#define _GNU_SOURCE #include <errno.h> #include <sched.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h>
int main(void) { long num_cores; cpu_set_t cpu_set; int ret;
num_cores = sysconf(_SC_NPROCESSORS_ONLN); CPU_ZERO(&cpu_set); CPU_SET(num_cores - 1, &cpu_set); errno = 0; ret = sched_setaffinity(getpid(), sizeof(cpu_set), &cpu_set); perror("sched_setaffinity"); return ret ? EXIT_FAILURE : EXIT_SUCCESS; }
The mistake is that suspend is handled in the action == CPU_DOWN_PREPARE_FROZEN case of the switch statement in cpuset_cpu_inactive().
However, the commit in question masked out CPU_TASKS_FROZEN from the action, making this case dead.
The fix is straightforward.
Signed-off-by: Omar Sandoval <osandov@osandov.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Borislav Petkov <bp@alien8.de> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Juri Lelli <juri.lelli@arm.com> Cc: Thomas Gleixner <tglx@linutronix.de> Fixes: 3c18d447b3b3 ("sched/core: Check for available DL bandwidth in cpuset_cpu_inactive()") Link: http://lkml.kernel.org/r/1cb5ecb3d6543c38cce5790387f336f54ec8e2bc.1430733960.git.osandov@osandov.com Signed-off-by: Ingo Molnar <mingo@kernel.org> --- kernel/sched/core.c | 28 ++++++++++++---------------- 1 file changed, 12 insertions(+), 16 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 34db9bf892a3..57bd333bc4ab 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -6999,27 +6999,23 @@ static int cpuset_cpu_inactive(struct notifier_block *nfb, unsigned long action, unsigned long flags; long cpu = (long)hcpu; struct dl_bw *dl_b; + bool overflow; + int cpus; - switch (action & ~CPU_TASKS_FROZEN) { + switch (action) { case CPU_DOWN_PREPARE: - /* explicitly allow suspend */ - if (!(action & CPU_TASKS_FROZEN)) { - bool overflow; - int cpus; - - rcu_read_lock_sched(); - dl_b = dl_bw_of(cpu); + rcu_read_lock_sched(); + dl_b = dl_bw_of(cpu); - raw_spin_lock_irqsave(&dl_b->lock, flags); - cpus = dl_bw_cpus(cpu); - overflow = __dl_overflow(dl_b, cpus, 0, 0); - raw_spin_unlock_irqrestore(&dl_b->lock, flags); + raw_spin_lock_irqsave(&dl_b->lock, flags); + cpus = dl_bw_cpus(cpu); + overflow = __dl_overflow(dl_b, cpus, 0, 0); + raw_spin_unlock_irqrestore(&dl_b->lock, flags); - rcu_read_unlock_sched(); + rcu_read_unlock_sched(); - if (overflow) - return notifier_from_errno(-EBUSY); - } + if (overflow) + return notifier_from_errno(-EBUSY); cpuset_update_active_cpus(false); break; case CPU_DOWN_PREPARE_FROZEN:
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