linux-kernel - Re: [PATCH] perf: Rewrite core context handling

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Date:   Wed, 7 Sep 2022 16:58:49 +0530
From:   Ravi Bangoria <ravi.bangoria@....com>
To:     peterz@...radead.org
Cc:     acme@...nel.org, alexander.shishkin@...ux.intel.com,
        jolsa@...hat.com, namhyung@...nel.org, songliubraving@...com,
        eranian@...gle.com, ak@...ux.intel.com, mark.rutland@....com,
        frederic@...nel.org, maddy@...ux.ibm.com, irogers@...gle.com,
        will@...nel.org, robh@...nel.org, mingo@...hat.com,
        catalin.marinas@....com, linux-arm-kernel@...ts.infradead.org,
        linux-perf-users@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        sandipan.das@....com, ananth.narayan@....com, kim.phillips@....com,
        santosh.shukla@....com, ravi.bangoria@....com
Subject: Re: [PATCH] perf: Rewrite core context handling

> -static void
> -ctx_flexible_sched_in(struct perf_event_context *ctx,
> -		      struct perf_cpu_context *cpuctx)
> +/* XXX .busy thingy from Peter's patch */
> +static void ctx_flexible_sched_in(struct perf_event_context *ctx, struct pmu *pmu)

This one turned out to be very easy. Given that, we iterate over each
pmu, we can just return error if we fail to schedule any flexible event.
(It wouldn't be straight forward like this if we needed to implement
pmu=NULL optimization.)

---
diff --git a/kernel/events/core.c b/kernel/events/core.c
index e0232e0bb74e..923656af73fe 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3751,6 +3751,7 @@ static int merge_sched_in(struct perf_event *event, void *data)
 			cpc = this_cpu_ptr(event->pmu_ctx->pmu->cpu_pmu_context);
 			perf_mux_hrtimer_restart(cpc);
 			group_update_userpage(event);
+			return -EBUSY;
 		}
 	}
 
@@ -3776,7 +3777,6 @@ static void ctx_pinned_sched_in(struct perf_event_context *ctx, struct pmu *pmu)
 	}
 }
 
-/* XXX .busy thingy from Peter's patch */
 static void ctx_flexible_sched_in(struct perf_event_context *ctx, struct pmu *pmu)
 {
 	struct perf_event_pmu_context *pmu_ctx;
---

Thanks,
Ravi