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Message-ID: <tip-84477336ec03f8061ffd6908da341e063e5d6d1f@git.kernel.org>
Date: Thu, 10 Mar 2016 03:07:24 -0800
From: tip-bot for Borislav Petkov <tipbot@...or.com>
To: linux-tip-commits@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, luto@...capital.net, luto@...nel.org,
hpa@...or.com, torvalds@...ux-foundation.org, mingo@...nel.org,
bp@...en8.de, bp@...e.de, ray.huang@....com, peterz@...radead.org,
tglx@...utronix.de, a.p.zijlstra@...llo.nl
Subject: [tip:x86/urgent] x86/delay: Avoid preemptible context checks in
delay_mwaitx()
Commit-ID: 84477336ec03f8061ffd6908da341e063e5d6d1f
Gitweb: http://git.kernel.org/tip/84477336ec03f8061ffd6908da341e063e5d6d1f
Author: Borislav Petkov <bp@...en8.de>
AuthorDate: Wed, 9 Mar 2016 21:56:22 +0100
Committer: Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 10 Mar 2016 11:27:12 +0100
x86/delay: Avoid preemptible context checks in delay_mwaitx()
We do use this_cpu_ptr(&cpu_tss) as a cacheline-aligned, seldomly
accessed per-cpu var as the MONITORX target in delay_mwaitx(). However,
when called in preemptible context, this_cpu_ptr -> smp_processor_id() ->
debug_smp_processor_id() fires:
BUG: using smp_processor_id() in preemptible [00000000] code: udevd/312
caller is delay_mwaitx+0x40/0xa0
But we don't care about that check - we only need cpu_tss as a MONITORX
target and it doesn't really matter which CPU's var we're touching as
we're going idle anyway. Fix that.
Suggested-by: Andy Lutomirski <luto@...nel.org>
Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Huang Rui <ray.huang@....com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: spg_linux_kernel@....com
Link: http://lkml.kernel.org/r/20160309205622.GG6564@pd.tnic
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
arch/x86/lib/delay.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/lib/delay.c b/arch/x86/lib/delay.c
index e912b2f..2f07c29 100644
--- a/arch/x86/lib/delay.c
+++ b/arch/x86/lib/delay.c
@@ -102,7 +102,7 @@ static void delay_mwaitx(unsigned long __loops)
* Use cpu_tss as a cacheline-aligned, seldomly
* accessed per-cpu variable as the monitor target.
*/
- __monitorx(this_cpu_ptr(&cpu_tss), 0, 0);
+ __monitorx(raw_cpu_ptr(&cpu_tss), 0, 0);
/*
* AMD, like Intel, supports the EAX hint and EAX=0xf
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