Messages in this thread Patch in this message | | | From | Sebastian Andrzej Siewior <> | Subject | [RFC PATCH] sched/cputime: drop local_irq_safe() in vtime_init_idle() | Date | Thu, 14 Apr 2016 14:29:14 +0200 |
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A while ago vtime_init_idle() used to invoke sched_clock_cpu() and had write_seqlock_irqsave() because sched_clock_cpu() required to be called with interrupts off. This requirement is written before the body of the function and was introduced in 2010 via c676329abb2b ("sched_clock: Add local_clock() API and improve documentation"). This requirement has been dropped in 2013 via ef08f0fff876 ("sched/clock: Remove local_irq_disable() from the clocks") but the body of the function still has the comment.
Now, vtime_init_idle() was converted from seqlock to seqcount via b7ce2277f087 ("sched/cputime: Convert vtime_seqlock to seqcount") and while doing so the IRQ-off region around sched_clock_cpu() was preserved while not strictly required (given the first part of this commit). A little later, sched_clock_cpu() was replaced with jiffies via ff9a9b4c4334 ("sched, time: Switch VIRT_CPU_ACCOUNTING_GEN to jiffy granularity"). Based on this events I assume it is safe to drop the local_irq_safe() section.
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Rik van Riel <riel@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> --- kernel/sched/cputime.c | 4 ---- 1 file changed, 4 deletions(-)
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index 75f98c5498d5..816cd4ef5873 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -785,14 +785,10 @@ void arch_vtime_task_switch(struct task_struct *prev) void vtime_init_idle(struct task_struct *t, int cpu) { - unsigned long flags; - - local_irq_save(flags); write_seqcount_begin(&t->vtime_seqcount); t->vtime_snap_whence = VTIME_SYS; t->vtime_snap = jiffies; write_seqcount_end(&t->vtime_seqcount); - local_irq_restore(flags); } cputime_t task_gtime(struct task_struct *t) -- 2.8.0.rc3
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