sched/fair: Fix the update of blocked load when newly idle

[Linux-MTD Mailing List]

Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=457be908c83637ee10bda085a23dc05afa3b14a0
Commit:     457be908c83637ee10bda085a23dc05afa3b14a0
Parent:     0b26351b910fb8fe6a056f8a1bbccabe50c0e19f
Author:     Vincent Guittot <vincent.guittot at linaro.org>
AuthorDate: Thu Apr 26 12:19:32 2018 +0200
Committer:  Ingo Molnar <mingo at kernel.org>
CommitDate: Thu May 3 07:38:03 2018 +0200

    sched/fair: Fix the update of blocked load when newly idle
    
    With commit:
    
      31e77c93e432 ("sched/fair: Update blocked load when newly idle")
    
    ... we release the rq->lock when updating blocked load of idle CPUs.
    
    This opens a time window during which another CPU can add a task to this
    CPU's cfs_rq.
    
    The check for newly added task of idle_balance() is not in the common path.
    Move the out label to include this check.
    
    Reported-by: Heiner Kallweit <hkallweit1 at gmail.com>
    Tested-by: Geert Uytterhoeven <geert+renesas at glider.be>
    Signed-off-by: Vincent Guittot <vincent.guittot at linaro.org>
    Signed-off-by: Peter Zijlstra (Intel) <peterz at infradead.org>
    Cc: Linus Torvalds <torvalds at linux-foundation.org>
    Cc: Paul E. McKenney <paulmck at linux.vnet.ibm.com>
    Cc: Peter Zijlstra <peterz at infradead.org>
    Cc: Thomas Gleixner <tglx at linutronix.de>
    Fixes: 31e77c93e432 ("sched/fair: Update blocked load when newly idle")
    Link: http://lkml.kernel.org/r/20180426103133.GA6953@linaro.org
    Signed-off-by: Ingo Molnar <mingo at kernel.org>
---
 kernel/sched/fair.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 54dc31e7ab9b..e3002e5ada31 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9847,6 +9847,7 @@ static int idle_balance(struct rq *this_rq, struct rq_flags *rf)
 	if (curr_cost > this_rq->max_idle_balance_cost)
 		this_rq->max_idle_balance_cost = curr_cost;
 
+out:
 	/*
 	 * While browsing the domains, we released the rq lock, a task could
 	 * have been enqueued in the meantime. Since we're not going idle,
@@ -9855,7 +9856,6 @@ static int idle_balance(struct rq *this_rq, struct rq_flags *rf)
 	if (this_rq->cfs.h_nr_running && !pulled_task)
 		pulled_task = 1;
 
-out:
 	/* Move the next balance forward */
 	if (time_after(this_rq->next_balance, next_balance))
 		this_rq->next_balance = next_balance;