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| author | Thomas Gleixner <tglx@linutronix.de> | 2016-07-12 18:33:56 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2016-07-13 14:58:20 +0200 |
| commit | d60585c5766e9620d5d83e2b25dc042c7bdada2c (patch) | |
| tree | ace0971cf7c7dcab339997d82ed635b8486dcb28 /kernel/sched | |
| parent | Linux 4.7-rc7 (diff) | |
| download | linux-d60585c5766e9620d5d83e2b25dc042c7bdada2c.tar.xz linux-d60585c5766e9620d5d83e2b25dc042c7bdada2c.zip | |
sched/core: Correct off by one bug in load migration calculation
The move of calc_load_migrate() from CPU_DEAD to CPU_DYING did not take into
account that the function is now called from a thread running on the outgoing
CPU. As a result a cpu unplug leakes a load of 1 into the global load
accounting mechanism.
Fix it by adjusting for the currently running thread which calls
calc_load_migrate().
Reported-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Cc: rt@linutronix.de
Cc: shreyas@linux.vnet.ibm.com
Fixes: e9cd8fa4fcfd: ("sched/migration: Move calc_load_migrate() into CPU_DYING")
Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1607121744350.4083@nanos
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched')
| -rw-r--r-- | kernel/sched/core.c | 6 | ||||
| -rw-r--r-- | kernel/sched/loadavg.c | 8 | ||||
| -rw-r--r-- | kernel/sched/sched.h | 2 |
3 files changed, 9 insertions, 7 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 51d7105f529a..97ee9ac7e97c 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5394,13 +5394,15 @@ void idle_task_exit(void) /* * Since this CPU is going 'away' for a while, fold any nr_active delta * we might have. Assumes we're called after migrate_tasks() so that the - * nr_active count is stable. + * nr_active count is stable. We need to take the teardown thread which + * is calling this into account, so we hand in adjust = 1 to the load + * calculation. * * Also see the comment "Global load-average calculations". */ static void calc_load_migrate(struct rq *rq) { - long delta = calc_load_fold_active(rq); + long delta = calc_load_fold_active(rq, 1); if (delta) atomic_long_add(delta, &calc_load_tasks); } diff --git a/kernel/sched/loadavg.c b/kernel/sched/loadavg.c index b0b93fd33af9..a2d6eb71f06b 100644 --- a/kernel/sched/loadavg.c +++ b/kernel/sched/loadavg.c @@ -78,11 +78,11 @@ void get_avenrun(unsigned long *loads, unsigned long offset, int shift) loads[2] = (avenrun[2] + offset) << shift; } -long calc_load_fold_active(struct rq *this_rq) +long calc_load_fold_active(struct rq *this_rq, long adjust) { long nr_active, delta = 0; - nr_active = this_rq->nr_running; + nr_active = this_rq->nr_running - adjust; nr_active += (long)this_rq->nr_uninterruptible; if (nr_active != this_rq->calc_load_active) { @@ -188,7 +188,7 @@ void calc_load_enter_idle(void) * We're going into NOHZ mode, if there's any pending delta, fold it * into the pending idle delta. */ - delta = calc_load_fold_active(this_rq); + delta = calc_load_fold_active(this_rq, 0); if (delta) { int idx = calc_load_write_idx(); @@ -389,7 +389,7 @@ void calc_global_load_tick(struct rq *this_rq) if (time_before(jiffies, this_rq->calc_load_update)) return; - delta = calc_load_fold_active(this_rq); + delta = calc_load_fold_active(this_rq, 0); if (delta) atomic_long_add(delta, &calc_load_tasks); diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 7cbeb92a1cb9..898c0d2f18fe 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -28,7 +28,7 @@ extern unsigned long calc_load_update; extern atomic_long_t calc_load_tasks; extern void calc_global_load_tick(struct rq *this_rq); -extern long calc_load_fold_active(struct rq *this_rq); +extern long calc_load_fold_active(struct rq *this_rq, long adjust); #ifdef CONFIG_SMP extern void cpu_load_update_active(struct rq *this_rq); |