From: Paul Mackerras Date: Tue, 12 May 2009 11:59:01 +0000 (+1000) Subject: perf_counter: call hw_perf_save_disable/restore around group_sched_in X-Git-Tag: v2.6.31-rc1~383^2~284 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e758a33d6fc5b9d6a3ae489863d04fcecad8120b;p=pandora-kernel.git perf_counter: call hw_perf_save_disable/restore around group_sched_in I noticed that when enabling a group via the PERF_COUNTER_IOC_ENABLE ioctl on the group leader, the counters weren't enabled and counting immediately on return from the ioctl, but did start counting a little while later (presumably after a context switch). The reason was that __perf_counter_enable calls group_sched_in which calls hw_perf_group_sched_in, which on powerpc assumes that the caller has called hw_perf_save_disable already. Until commit 46d686c6 ("perf_counter: put whole group on when enabling group leader") it was true that all callers of group_sched_in had called hw_perf_save_disable first, and the powerpc hw_perf_group_sched_in relies on that (there isn't an x86 version). This fixes the problem by putting calls to hw_perf_save_disable / hw_perf_restore around the calls to group_sched_in and counter_sched_in in __perf_counter_enable. Having the calls to hw_perf_save_disable/restore around the counter_sched_in call is harmless and makes this call consistent with the other call sites of counter_sched_in, which have all called hw_perf_save_disable first. [ Impact: more precise counter group disable/enable functionality ] Signed-off-by: Paul Mackerras Cc: Peter Zijlstra Cc: Corey Ashford LKML-Reference: <18953.25733.53359.147452@cargo.ozlabs.ibm.com> Signed-off-by: Ingo Molnar --- Reading git-diff-tree failed