Messages in this thread | | | Date | Fri, 29 May 2009 10:59:16 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH RFC] perf_counter: Don't swap contexts containing locked mutex |
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* Peter Zijlstra <peterz@infradead.org> wrote:
> On Fri, 2009-05-29 at 10:13 +0200, Peter Zijlstra wrote: > > On Fri, 2009-05-29 at 10:06 +0200, Peter Zijlstra wrote: > > > > > static struct perf_counter_ctx *pin_ctx(struct perf_counter *counter, u64 *old_gen) > > > { > > > struct perf_counter_context *ctx; > > > unsigned long flags; > > > > > > rcu_read_lock(); > > > retry: > > > ctx = rcu_dereference(counter->ctx); > > > spin_lock_irqsave(&ctx->lock, flags); > > > if (ctx != rcu_dereference(counter->ctx)) > > > goto retry; > > > > > > *old_gen = ctx->generation; > > > ctx->generation = ~0ULL; > > > spin_unlock_irqrestore(&ctx->lock, flags); > > > rcu_read_unlock(); > > > > > > return ctx; > > > } > > > > > > static void unpin_ctx(struct perf_counter_ctx *ctx, u64 old_gen) > > > { > > > unsigned long flags; > > > > > > spin_lock_irqsave(&ctx->lock, flags); > > > ctx->generation = old_gen; > > > spin_unlock_irqrestore(&ctx->lock, flags); > > > } > > > > OK, I think I got this wrong, counter->ctx isn't the problem. > > task->perf_counter_ctx is. > > > > Still would be nice to write it in the above form. I'll go over the code > > again to see who else might want it. > > OK, I went over the code, and your patch does indeed cover the few > spots we need. It was just my brain going haywire and auditing the > wrong pattern.
ok - i'll try this with my 'perf stat make -j' workload that quickly locks up on a Nehalem. (bug introduced by the context switch optimizations)
Ingo
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