On Wed, Feb 05, 2014 at 06:19:27PM +0100, Stephane Eranian wrote: > On Fri, Jan 3, 2014 at 6:48 AM, Yan, Zheng <zheng.z....@intel.com> wrote: > > If two tasks were both forked from the same parent task, Events in their > > perf > > task contexts can be the same. Perf core optimizes context switch oout in > > this > > case. > > > > Previous patch inroduces pmu specific data. The data is task specific, so we > > should switch the data even when context switch is optimized out. > > > Reviwed-by: Stephane Eranian <eran...@google.com>
You should look again.. that xchg() is an atomic op and a total waste of time since the assignment back onto ctx->task_ctx_data is non-atomic. Complete fail there. > > Signed-off-by: Yan, Zheng <zheng.z....@intel.com> > > --- > > kernel/events/core.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/kernel/events/core.c b/kernel/events/core.c > > index b6650ab..d6d8dea 100644 > > --- a/kernel/events/core.c > > +++ b/kernel/events/core.c > > @@ -2319,6 +2319,8 @@ static void perf_event_context_sched_out(struct > > task_struct *task, int ctxn, > > next->perf_event_ctxp[ctxn] = ctx; > > ctx->task = next; > > next_ctx->task = task; > > + ctx->task_ctx_data = xchg(&next_ctx->task_ctx_data, > > + ctx->task_ctx_data); > > do_switch = 0; > > > > perf_event_sync_stat(ctx, next_ctx); > > -- > > 1.8.4.2 > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
