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>
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@ -5394,13 +5394,15 @@ void idle_task_exit(void)
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/*
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/*
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* Since this CPU is going 'away' for a while, fold any nr_active delta
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* Since this CPU is going 'away' for a while, fold any nr_active delta
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* we might have. Assumes we're called after migrate_tasks() so that the
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* we might have. Assumes we're called after migrate_tasks() so that the
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* nr_active count is stable.
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* nr_active count is stable. We need to take the teardown thread which
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* is calling this into account, so we hand in adjust = 1 to the load
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* calculation.
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*
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*
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* Also see the comment "Global load-average calculations".
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* Also see the comment "Global load-average calculations".
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*/
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*/
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static void calc_load_migrate(struct rq *rq)
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static void calc_load_migrate(struct rq *rq)
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{
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{
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long delta = calc_load_fold_active(rq);
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long delta = calc_load_fold_active(rq, 1);
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if (delta)
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if (delta)
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atomic_long_add(delta, &calc_load_tasks);
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atomic_long_add(delta, &calc_load_tasks);
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}
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}
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@ -78,11 +78,11 @@ void get_avenrun(unsigned long *loads, unsigned long offset, int shift)
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loads[2] = (avenrun[2] + offset) << shift;
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loads[2] = (avenrun[2] + offset) << shift;
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}
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}
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long calc_load_fold_active(struct rq *this_rq)
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long calc_load_fold_active(struct rq *this_rq, long adjust)
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{
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{
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long nr_active, delta = 0;
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long nr_active, delta = 0;
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nr_active = this_rq->nr_running;
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nr_active = this_rq->nr_running - adjust;
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nr_active += (long)this_rq->nr_uninterruptible;
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nr_active += (long)this_rq->nr_uninterruptible;
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if (nr_active != this_rq->calc_load_active) {
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if (nr_active != this_rq->calc_load_active) {
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@ -188,7 +188,7 @@ void calc_load_enter_idle(void)
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* We're going into NOHZ mode, if there's any pending delta, fold it
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* We're going into NOHZ mode, if there's any pending delta, fold it
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* into the pending idle delta.
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* into the pending idle delta.
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*/
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*/
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delta = calc_load_fold_active(this_rq);
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delta = calc_load_fold_active(this_rq, 0);
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if (delta) {
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if (delta) {
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int idx = calc_load_write_idx();
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int idx = calc_load_write_idx();
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@ -389,7 +389,7 @@ void calc_global_load_tick(struct rq *this_rq)
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if (time_before(jiffies, this_rq->calc_load_update))
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if (time_before(jiffies, this_rq->calc_load_update))
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return;
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return;
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delta = calc_load_fold_active(this_rq);
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delta = calc_load_fold_active(this_rq, 0);
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if (delta)
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if (delta)
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atomic_long_add(delta, &calc_load_tasks);
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atomic_long_add(delta, &calc_load_tasks);
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@ -28,7 +28,7 @@ extern unsigned long calc_load_update;
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extern atomic_long_t calc_load_tasks;
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extern atomic_long_t calc_load_tasks;
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extern void calc_global_load_tick(struct rq *this_rq);
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extern void calc_global_load_tick(struct rq *this_rq);
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extern long calc_load_fold_active(struct rq *this_rq);
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extern long calc_load_fold_active(struct rq *this_rq, long adjust);
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#ifdef CONFIG_SMP
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#ifdef CONFIG_SMP
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extern void cpu_load_update_active(struct rq *this_rq);
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extern void cpu_load_update_active(struct rq *this_rq);
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