Re: [PATCH 08/11] membarrier: Provide core serializing command (v2)
flat view
From: Peter Zijlstra <peterz@infradead.org>
Date: 2018-01-29 18:04:59
Also in:
linux-arch, lkml
On Tue, Jan 23, 2018 at 10:57:30AM -0500, Mathieu Desnoyers wrote:
quoted hunk ↗ jump to hunk
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index f38c4c7e256a..041893128f51 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c@@ -2662,9 +2662,13 @@ static struct rq *finish_task_switch(struct task_struct *prev) * thread, mmdrop()'s implicit full barrier is required by the * membarrier system call, because the current active_mm can * become the current mm without going through switch_mm(). + * membarrier also requires a core serializing instruction + * before going back to user-space after storing to rq->curr. */ - if (mm) + if (mm) { + membarrier_mm_sync_core_before_usermode(mm); mmdrop(mm); + }
*confused*, when we switch from process A to process B, context_switch() will not set rq->prev_mm and the above mm will be NULL and we'll not pass through your_function_names_are_waaay_too_long and we'll not get cookies. And if there's anything more complicated going on, the comment/changelog are not adequate.
if (unlikely(prev_state == TASK_DEAD)) {
if (prev->sched_class->task_dead)
prev->sched_class->task_dead(prev);