From: Peter Zijlstra <peterz@infradead.org>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Boqun Feng <boqun.feng@gmail.com>,
linux-kernel@vger.kernel.org, Will Deacon <will@kernel.org>,
"Paul E . McKenney" <paulmck@kernel.org>,
Nicholas Piggin <npiggin@gmail.com>,
Andy Lutomirski <luto@amacapital.net>,
Thomas Gleixner <tglx@linutronix.de>,
Linus Torvalds <torvalds@linux-foundation.org>,
Alan Stern <stern@rowland.harvard.edu>,
linux-mm@kvack.org
Subject: Re: [PATCH 1/3] sched: fix exit_mm vs membarrier (v4)
Date: Tue, 20 Oct 2020 16:36:48 +0200 [thread overview]
Message-ID: <20201020143648.GU2628@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20201020134715.13909-2-mathieu.desnoyers@efficios.com>
On Tue, Oct 20, 2020 at 09:47:13AM -0400, Mathieu Desnoyers wrote:
> +void membarrier_update_current_mm(struct mm_struct *next_mm)
> +{
> + struct rq *rq = this_rq();
> + int membarrier_state = 0;
> +
> + if (next_mm)
> + membarrier_state = atomic_read(&next_mm->membarrier_state);
> + if (READ_ONCE(rq->membarrier_state) == membarrier_state)
> + return;
> + WRITE_ONCE(rq->membarrier_state, membarrier_state);
> +}
This is suspisioucly similar to membarrier_switch_mm().
Would something like so make sense?
---
--- a/kernel/sched/membarrier.c
+++ b/kernel/sched/membarrier.c
@@ -206,14 +206,7 @@ void membarrier_exec_mmap(struct mm_stru
void membarrier_update_current_mm(struct mm_struct *next_mm)
{
- struct rq *rq = this_rq();
- int membarrier_state = 0;
-
- if (next_mm)
- membarrier_state = atomic_read(&next_mm->membarrier_state);
- if (READ_ONCE(rq->membarrier_state) == membarrier_state)
- return;
- WRITE_ONCE(rq->membarrier_state, membarrier_state);
+ membarrier_switch_mm(this_rq(), NULL, next_mm);
}
static int membarrier_global_expedited(void)
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index d2621155393c..3d589c2ffd28 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2645,12 +2645,14 @@ static inline void membarrier_switch_mm(struct rq *rq,
struct mm_struct *prev_mm,
struct mm_struct *next_mm)
{
- int membarrier_state;
+ int membarrier_state = 0;
if (prev_mm == next_mm)
return;
- membarrier_state = atomic_read(&next_mm->membarrier_state);
+ if (next_mm)
+ membarrier_state = atomic_read(&next_mm->membarrier_state);
+
if (READ_ONCE(rq->membarrier_state) == membarrier_state)
return;
next prev parent reply other threads:[~2020-10-20 14:36 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20201020134715.13909-1-mathieu.desnoyers@efficios.com>
2020-10-20 13:47 ` [PATCH 1/3] sched: fix exit_mm vs membarrier (v4) Mathieu Desnoyers
2020-10-20 14:36 ` Peter Zijlstra [this message]
2020-10-20 14:59 ` Mathieu Desnoyers
2020-10-22 6:51 ` Boqun Feng
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