Commit be958bdc authored Nov 25, 2015 by Peter Zijlstra Committed by Ingo Molnar Jan 06, 2016

sched/core: Fix unserialized r-m-w scribbling stuff



Some of the sched bitfieds (notably sched_reset_on_fork) can be set
on other than current, this can cause the r-m-w to race with other
updates.

Since all the sched bits are serialized by scheduler locks, pull them
in a separate word.

Reported-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: akpm@linux-foundation.org
Cc: hannes@cmpxchg.org
Cc: mhocko@kernel.org
Cc: vdavydov@parallels.com
Link: http://lkml.kernel.org/r/20151125150207.GM11639@twins.programming.kicks-ass.net


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 570f5241

include/linux/sched.h

+6 −5

Original line number	Diff line number	Diff line
		@@ -1455,14 +1455,15 @@ struct task_struct {
		/* Used for emulating ABI behavior of previous Linux versions */
		unsigned int personality;

		unsigned in_execve:1; /* Tell the LSMs that the process is doing an
		* execve */
		unsigned in_iowait:1;

		/* Revert to default priority/policy when forking */
		/* scheduler bits, serialized by scheduler locks */
		unsigned sched_reset_on_fork:1;
		unsigned sched_contributes_to_load:1;
		unsigned sched_migrated:1;
		unsigned :0; /* force alignment to the next boundary */

		/* unserialized, strictly 'current' */
		unsigned in_execve:1; /* bit to tell LSMs we're in execve */
		unsigned in_iowait:1;
		#ifdef CONFIG_MEMCG
		unsigned memcg_may_oom:1;
		#endif

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