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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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bfd9b2b5f8
__schedule() disables preemption during its job and re-enables it afterward without doing a preemption check to avoid recursion. But if an event happens after the context switch which requires rescheduling, we need to check again if a task of a higher priority needs the CPU. A preempt irq can raise such a situation. To handle that, __schedule() loops on need_resched(). But preempt_schedule_*() functions, which call __schedule(), also loop on need_resched() to handle missed preempt irqs. Hence we end up with the same loop happening twice. Lets simplify that by attributing the need_resched() loop responsibility to all __schedule() callers. There is a risk that the outer loop now handles reschedules that used to be handled by the inner loop with the added overhead of caller details (inc/dec of PREEMPT_ACTIVE, irq save/restore) but assuming those inner rescheduling loop weren't too frequent, this shouldn't matter. Especially since the whole preemption path is now losing one loop in any case. Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Link: http://lkml.kernel.org/r/1422404652-29067-2-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org> |
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| .. | ||
| auto_group.c | ||
| auto_group.h | ||
| clock.c | ||
| completion.c | ||
| core.c | ||
| cpuacct.c | ||
| cpuacct.h | ||
| cpudeadline.c | ||
| cpudeadline.h | ||
| cpupri.c | ||
| cpupri.h | ||
| cputime.c | ||
| deadline.c | ||
| debug.c | ||
| fair.c | ||
| features.h | ||
| idle_task.c | ||
| idle.c | ||
| Makefile | ||
| proc.c | ||
| rt.c | ||
| sched.h | ||
| stats.c | ||
| stats.h | ||
| stop_task.c | ||
| wait.c | ||