From: Don Zickus Date: Wed, 27 Apr 2011 10:32:33 +0000 (-0400) Subject: perf, x86, nmi: Move LVT un-masking into irq handlers X-Git-Tag: v2.6.39-rc6~17^2 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2bce5daca28346f19c190dbdb5542c9fe3e8c6e6;p=pandora-kernel.git perf, x86, nmi: Move LVT un-masking into irq handlers 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: Shaun Ruffell Signed-off-by: Don Zickus Cc: Cyrill Gorcunov Link: http://lkml.kernel.org/r/1303900353-10242-1-git-send-email-dzickus@redhat.com Signed-off-by: Ingo Molnar CC: Cyrill Gorcunov --- Reading git-diff-tree failed