1. 01 5月, 2011 1 次提交
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      perf, x86, nmi: Move LVT un-masking into irq handlers · 2bce5dac
      Don Zickus 提交于
      It was noticed that P4 machines were generating double NMIs for
      each perf event.  These extra NMIs lead to 'Dazed and confused'
      messages on the screen.
      
      I tracked this down to a P4 quirk that said the overflow bit had
      to be cleared before re-enabling the apic LVT mask.  My first
      attempt was to move the un-masking inside the perf nmi handler
      from before the chipset NMI handler to after.
      
      This broke Nehalem boxes that seem to like the unmasking before
      the counters themselves are re-enabled.
      
      In order to keep this change simple for 2.6.39, I decided to
      just simply move the apic LVT un-masking to the beginning of all
      the chipset NMI handlers, with the exception of Pentium4's to
      fix the double NMI issue.
      
      Later on we can move the un-masking to later in the handlers to
      save a number of 'extra' NMIs on those particular chipsets.
      
      I tested this change on a P4 machine, an AMD machine, a Nehalem
      box, and a core2quad box.  'perf top' worked correctly along
      with various other small 'perf record' runs.  Anything high
      stress breaks all the machines but that is a different problem.
      
      Thanks to various people for testing different versions of this
      patch.
      Reported-and-tested-by: NShaun Ruffell <sruffell@digium.com>
      Signed-off-by: NDon Zickus <dzickus@redhat.com>
      Cc: Cyrill Gorcunov <gorcunov@gmail.com>
      Link: http://lkml.kernel.org/r/1303900353-10242-1-git-send-email-dzickus@redhat.comSigned-off-by: NIngo Molnar <mingo@elte.hu>
      CC: Cyrill Gorcunov <gorcunov@gmail.com>
      2bce5dac