x86/delay: Avoid preemptible context checks in delay_mwaitx()
authorBorislav Petkov <bp@alien8.de>
Wed, 9 Mar 2016 20:56:22 +0000 (21:56 +0100)
committerIngo Molnar <mingo@kernel.org>
Thu, 10 Mar 2016 10:27:12 +0000 (11:27 +0100)
commit84477336ec03f8061ffd6908da341e063e5d6d1f
treec5b17f64a9fd0f611810039705d0cbe5741ca6de
parenta65050c6f17e52442716138d48d0a47301a8344b
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@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>
arch/x86/lib/delay.c