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 <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Cc: Dmitry Vyukov <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Sasha Levin <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: Dmitry Vyukov <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> 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 <[email protected]> --- 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; _______________________________________________ Devel mailing list [email protected] https://lists.openvz.org/mailman/listinfo/devel
