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x86/delay: Avoid preemptible context checks in delay_mwaitx()

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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@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Huang Rui <ray.huang@amd.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: spg_linux_kernel@amd.com
Link: http://lkml.kernel.org/r/20160309205622.GG6564@pd.tnic
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Borislav Petkov 2016-03-09 21:56:22 +01:00 committed by Ingo Molnar
parent a65050c6f1
commit 84477336ec
1 changed files with 1 additions and 1 deletions
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arch/x86/lib/delay.c
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@ -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