3.16.39-rc1 review patch. If anyone has any objections, please let me know.
------------------ From: Wanpeng Li <[email protected]> commit 3d89e5478bf550a50c99e93adf659369798263b0 upstream. Commit: e9532e69b8d1 ("sched/cputime: Fix steal time accounting vs. CPU hotplug") ... set rq->prev_* to 0 after a CPU hotplug comes back, in order to fix the case where (after CPU hotplug) steal time is smaller than rq->prev_steal_time. However, this should never happen. Steal time was only smaller because of the KVM-specific bug fixed by the previous patch. Worse, the previous patch triggers a bug on CPU hot-unplug/plug operation: because rq->prev_steal_time is cleared, all of the CPU's past steal time will be accounted again on hot-plug. Since the root cause has been fixed, we can just revert commit e9532e69b8d1. Signed-off-by: Wanpeng Li <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Acked-by: Paolo Bonzini <[email protected]> Cc: Frederic Weisbecker <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Mike Galbraith <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Radim Krčmář <[email protected]> Cc: Rik van Riel <[email protected]> Cc: Thomas Gleixner <[email protected]> Fixes: 'commit e9532e69b8d1 ("sched/cputime: Fix steal time accounting vs. CPU hotplug")' Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings <[email protected]> --- kernel/sched/core.c | 1 - kernel/sched/sched.h | 13 ------------- 2 files changed, 14 deletions(-) --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5147,7 +5147,6 @@ migration_call(struct notifier_block *nf case CPU_UP_PREPARE: rq->calc_load_update = calc_load_update; - account_reset_rq(rq); break; case CPU_ONLINE: --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1563,16 +1563,3 @@ static inline u64 irq_time_read(int cpu) } #endif /* CONFIG_64BIT */ #endif /* CONFIG_IRQ_TIME_ACCOUNTING */ - -static inline void account_reset_rq(struct rq *rq) -{ -#ifdef CONFIG_IRQ_TIME_ACCOUNTING - rq->prev_irq_time = 0; -#endif -#ifdef CONFIG_PARAVIRT - rq->prev_steal_time = 0; -#endif -#ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING - rq->prev_steal_time_rq = 0; -#endif -}
