linux-kernel - [PATCH] mm: trace tlb flush after disabling preemption in try_to_unmap

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Message-Id: <1437075339-32715-1-git-send-email-sasha.levin@oracle.com>
Date:	Thu, 16 Jul 2015 15:35:39 -0400
From:	Sasha Levin <sasha.levin@...cle.com>
To:	akpm@...ux-foundation.org, mgorman@...e.de
Cc:	mhocko@...e.cz, riel@...hat.com, mingo@...nel.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Sasha Levin <sasha.levin@...cle.com>
Subject: [PATCH] mm: trace tlb flush after disabling preemption in try_to_unmap_flush

Commit "mm: send one IPI per CPU to TLB flush all entries after unmapping
pages" added a trace_tlb_flush() while preemption was still enabled. This
means that we'll access smp_processor_id() which in turn will get us quite
a few warnings.

Fix it by moving the trace to where the preemption is disabled, one line
down.

Signed-off-by: Sasha Levin <sasha.levin@...cle.com>
---

The diff is all lies: I've moved trace_tlb_flush() one line down rather
than get_cpu() a line up ;)

 mm/rmap.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/rmap.c b/mm/rmap.c
index 30812e9..63ba46c 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -613,9 +613,10 @@ void try_to_unmap_flush(void)
 	if (!tlb_ubc->flush_required)
 		return;
 
+	cpu = get_cpu();
+
 	trace_tlb_flush(TLB_REMOTE_SHOOTDOWN, -1UL);
 
-	cpu = get_cpu();
 	if (cpumask_test_cpu(cpu, &tlb_ubc->cpumask))
 		percpu_flush_tlb_batch_pages(&tlb_ubc->cpumask);
 
-- 
1.7.10.4

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