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authorJiri Olsa <jolsa@redhat.com>2012-05-23 15:13:02 +0400
committerIngo Molnar <mingo@kernel.org>2012-05-23 19:40:51 +0400
commitab0cce560ef177bdc7a8f73e9962be9d829a7b2c (patch)
treed9875b21c42862201624eb7d9ea2c36f4ea4035d /tools
parent26252ea675663d1bc6747125fcaa2b7cc4ed8a03 (diff)
downloadlinux-ab0cce560ef177bdc7a8f73e9962be9d829a7b2c.tar.xz
Revert "sched, perf: Use a single callback into the scheduler"
This reverts commit cb04ff9ac424 ("sched, perf: Use a single callback into the scheduler"). Before this change was introduced, the process switch worked like this (wrt. to perf event schedule): schedule (prev, next) - schedule out all perf events for prev - switch to next - schedule in all perf events for current (next) After the commit, the process switch looks like: schedule (prev, next) - schedule out all perf events for prev - schedule in all perf events for (next) - switch to next The problem is, that after we schedule perf events in, the pmu is enabled and we can receive events even before we make the switch to next - so "current" still being prev process (event SAMPLE data are filled based on the value of the "current" process). Thats exactly what we see for test__PERF_RECORD test. We receive SAMPLES with PID of the process that our tracee is scheduled from. Discussed with Peter Zijlstra: > Bah!, yeah I guess reverting is the right thing for now. Sad > though. > > So by having the two hooks we have a black-spot between them > where we receive no events at all, this black-spot covers the > hand-over of current and we thus don't receive the 'wrong' > events. > > I rather liked we could do away with both that black-spot and > clean up the code a little, but apparently people rely on it. Signed-off-by: Jiri Olsa <jolsa@redhat.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: acme@redhat.com Cc: paulus@samba.org Cc: cjashfor@linux.vnet.ibm.com Cc: fweisbec@gmail.com Cc: eranian@google.com Link: http://lkml.kernel.org/r/20120523111302.GC1638@m.brq.redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
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