* Gabriele Mazzotta <gabriele....@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 <osan...@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 <osan...@osandov.com>
Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
Cc: Borislav Petkov <b...@alien8.de>
Cc: H. Peter Anvin <h...@zytor.com>
Cc: Juri Lelli <juri.le...@arm.com>
Cc: Thomas Gleixner <t...@linutronix.de>
Fixes: 3c18d447b3b3 ("sched/core: Check for available DL bandwidth in
cpuset_cpu_inactive()")
Link:
http://lkml.kernel.org/r/1cb5ecb3d6543c38cce5790387f336f54ec8e2bc.1430733960.git.osan...@osandov.com
Signed-off-by: Ingo Molnar <mi...@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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