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>

1 files 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: