Port commit be958bdc96f18bc1356177bbb79d46ea0c037b96 from mainstream.
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 <t...@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
Cc: Dmitry Vyukov <dvyu...@google.com>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Sasha Levin <sasha.le...@oracle.com>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: a...@linux-foundation.org
Cc: han...@cmpxchg.org
Cc: mho...@kernel.org
Cc: Dmitry Vyukov <dvyu...@google.com>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Really the below 4 bits are protected by different locks:
unsigned sched_reset_on_fork:1; rq pi
unsigned sched_contributes_to_load:1; pi
unsigned sched_interruptible_sleep:1; pi
unsigned woken_while_running:1; rq
But we may say, all of them are protected by rq lock,
because sched_contributes_to_load and sched_interruptible_sleep
are modified in try_to_wake_up(), when task is not on rq,
so nobody can modify sched_reset_on_fork and woken_while_running
this moment.
Thus we won't use one more bitfield and save a memory of one word.
Signed-off-by: Kirill Tkhai <ktk...@virtuozzo.com>
---
include/linux/sched.h | 21 +++++++++++----------
1 file changed, 11 insertions(+), 10 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 4bbd391..81dc3d7 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1231,21 +1231,22 @@ struct task_struct {
/* Used for emulating ABI behavior of previous Linux versions */
unsigned int personality;
+ /* scheduler bits, serialized by rq lock: */
+ unsigned sched_reset_on_fork:1;
+ /* Two below are really protected by pi_lock, but they are modified in
+ * the place where nobody else can modify other fields using rq->lock
*/
+ unsigned sched_contributes_to_load:1;
+ unsigned sched_interruptible_sleep:1;
+ unsigned woken_while_running:1;
+ unsigned :0; /* force alignment to the next boundary */
+
+ /* unserialized, strictly 'current' */
unsigned did_exec:1;
unsigned in_execve:1; /* Tell the LSMs that the process is doing an
* execve */
unsigned in_iowait:1;
unsigned did_ve_enter:1;
-
- /* task may not gain privileges */
- unsigned no_new_privs:1;
-
- /* Revert to default priority/policy when forking */
- unsigned sched_reset_on_fork:1;
- unsigned sched_contributes_to_load:1;
- unsigned sched_interruptible_sleep:1;
-
- unsigned woken_while_running:1;
+ unsigned no_new_privs:1; /* task may not gain privileges */
unsigned may_throttle:1;
pid_t pid;
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