Ignore this, I'll better split this patch into two.
On 15.01.2016 18:09, Kirill Tkhai wrote: > 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 (patch makes this) > > 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 +++++++++++---------- > kernel/sched/core.c | 5 ++--- > 2 files changed, 13 insertions(+), 13 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; > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index c8ac8bd..f61a4d1 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -1616,6 +1616,7 @@ static int ttwu_remote(struct task_struct *p, int > wake_flags) > rq = __task_rq_lock(p); > if (p->on_rq) { > ttwu_do_wakeup(rq, p, wake_flags); > + p->woken_while_running = 1; > ret = 1; > } > __task_rq_unlock(rq); > @@ -1739,10 +1740,8 @@ try_to_wake_up(struct task_struct *p, unsigned int > state, int wake_flags) > success = 1; /* we're going to change ->state */ > cpu = task_cpu(p); > > - if (p->on_rq && ttwu_remote(p, wake_flags)) { > - p->woken_while_running = 1; > + if (p->on_rq && ttwu_remote(p, wake_flags)) > goto stat; > - } > > #ifdef CONFIG_SMP > /* > > _______________________________________________ > Devel mailing list > [email protected] > https://lists.openvz.org/mailman/listinfo/devel > _______________________________________________ Devel mailing list [email protected] https://lists.openvz.org/mailman/listinfo/devel
