Messages in this thread Patch in this message | | | Date | Wed, 23 Sep 2009 16:10:34 +0800 | From | Xiao Guangrong <> | Subject | [PATCH 1/2] perf_counter: cleanup for __perf_event_sched_*() |
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Paul Mackerras says:
"Actually, looking at this more closely, it has to be a group leader anyway since it's at the top level of ctx->group_list. In fact I see four places where we do:
list_for_each_entry(event, &ctx->group_list, group_entry) { if (event == event->group_leader) ...
or the equivalent, three of which appear to have been introduced by afedadf2 ("perf_counter: Optimize sched in/out of counters") back in May by Peter Z.
As far as I can see the if () is superfluous in each case (a singleton event will be a group of 1 and will have its group_leader pointing to itself)."
[Can be found at http://marc.info/?l=linux-kernel&m=125361238901442&w=2]
So, this patch fix it.
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com> --- kernel/perf_event.c | 41 +++++++++++++++++++++++------------------ 1 files changed, 23 insertions(+), 18 deletions(-)
diff --git a/kernel/perf_event.c b/kernel/perf_event.c index 76ac4db..9ca975a 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -1032,10 +1032,13 @@ void __perf_event_sched_out(struct perf_event_context *ctx, perf_disable(); if (ctx->nr_active) { list_for_each_entry(event, &ctx->group_list, group_entry) { - if (event != event->group_leader) - event_sched_out(event, cpuctx, ctx); - else - group_sched_out(event, cpuctx, ctx); + + /* + * It has to be a group leader since it's at the top + * level of ctx->group_list + */ + WARN_ON_ONCE(event != event->group_leader); + group_sched_out(event, cpuctx, ctx); } } perf_enable(); @@ -1258,12 +1261,14 @@ __perf_event_sched_in(struct perf_event_context *ctx, if (event->cpu != -1 && event->cpu != cpu) continue; - if (event != event->group_leader) - event_sched_in(event, cpuctx, ctx, cpu); - else { - if (group_can_go_on(event, cpuctx, 1)) - group_sched_in(event, cpuctx, ctx, cpu); - } + /* + * It has to be a group leader since it's at the top + * level of ctx->group_list + */ + WARN_ON_ONCE(event != event->group_leader); + + if (group_can_go_on(event, cpuctx, 1)) + group_sched_in(event, cpuctx, ctx, cpu); /* * If this pinned group hasn't been scheduled, @@ -1291,15 +1296,15 @@ __perf_event_sched_in(struct perf_event_context *ctx, if (event->cpu != -1 && event->cpu != cpu) continue; - if (event != event->group_leader) { - if (event_sched_in(event, cpuctx, ctx, cpu)) + /* + * It has to be a group leader since it's at the top + * level of ctx->group_list + */ + WARN_ON_ONCE(event != event->group_leader); + + if (group_can_go_on(event, cpuctx, can_add_hw)) + if (group_sched_in(event, cpuctx, ctx, cpu)) can_add_hw = 0; - } else { - if (group_can_go_on(event, cpuctx, can_add_hw)) { - if (group_sched_in(event, cpuctx, ctx, cpu)) - can_add_hw = 0; - } - } } perf_enable(); out: -- 1.6.1.2
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