From: Thomas Richter <tmricht@linux.ibm.com>
Date: Tue, 8 Oct 2024 12:51:10 +0000 (+0200)
Subject: s390/cpum_sf: Do not re-enable event after deletion
X-Git-Tag: v6.13-rc1~206^2~74
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=db417646fecd10b330c9dd611a39999520553bf2;p=thirdparty%2Fkernel%2Flinux.git

s390/cpum_sf: Do not re-enable event after deletion

Event delete removes an event from the event list, but common
code invokes the PMU's enable function later on. This happens
in event_sched_out() and leads to the following call sequence:

  event_sched_out()
  +--> cpumsf_pmu_del()
  +--> cpumsf_pmu_enable()

In cpumsf_pmu_enable() return immediately when the event is not
active. Also remove an unneeded if clause. That if() statement
is only reached when flag PMU_F_IN_USE has been set in
cpumsf_pmu_add(). And this function also sets cpuhw->event
to a valid value.

Remove WARN_ON_ONCE() statement which never triggered.

Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Reviewed-by: Hendrik Brueckner <brueckner@linux.ibm.com>
Acked-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
---

diff --git a/arch/s390/kernel/perf_cpum_sf.c b/arch/s390/kernel/perf_cpum_sf.c
index e806693c8473d..c916d04815db0 100644
--- a/arch/s390/kernel/perf_cpum_sf.c
+++ b/arch/s390/kernel/perf_cpum_sf.c
@@ -910,10 +910,14 @@ static void cpumsf_pmu_enable(struct pmu *pmu)
 	struct hw_perf_event *hwc;
 	int err;
 
-	if (cpuhw->flags & PMU_F_ENABLED)
-		return;
-
-	if (cpuhw->flags & PMU_F_ERR_MASK)
+	/*
+	 * Event must be
+	 * - added/started on this CPU (PMU_F_IN_USE set)
+	 * - and CPU must be available (PMU_F_RESERVED set)
+	 * - and not already enabled (PMU_F_ENABLED not set)
+	 * - and not in error condition (PMU_F_ERR_MASK not set)
+	 */
+	if (cpuhw->flags != (PMU_F_IN_USE | PMU_F_RESERVED))
 		return;
 
 	/* Check whether to extent the sampling buffer.
@@ -927,19 +931,16 @@ static void cpumsf_pmu_enable(struct pmu *pmu)
 	 * facility, but it can be fully re-enabled using sampling controls that
 	 * have been saved in cpumsf_pmu_disable().
 	 */
-	if (cpuhw->event) {
-		hwc = &cpuhw->event->hw;
-		if (!(SAMPL_DIAG_MODE(hwc))) {
-			/*
-			 * Account number of overflow-designated
-			 * buffer extents
-			 */
-			sfb_account_overflows(cpuhw, hwc);
-			extend_sampling_buffer(&cpuhw->sfb, hwc);
-		}
-		/* Rate may be adjusted with ioctl() */
-		cpuhw->lsctl.interval = SAMPL_RATE(hwc);
+	hwc = &cpuhw->event->hw;
+	if (!(SAMPL_DIAG_MODE(hwc))) {
+		/*
+		 * Account number of overflow-designated buffer extents
+		 */
+		sfb_account_overflows(cpuhw, hwc);
+		extend_sampling_buffer(&cpuhw->sfb, hwc);
 	}
+	/* Rate may be adjusted with ioctl() */
+	cpuhw->lsctl.interval = SAMPL_RATE(hwc);
 
 	/* (Re)enable the PMU and sampling facility */
 	err = lsctl(&cpuhw->lsctl);
@@ -1954,13 +1955,12 @@ static void cpumf_measurement_alert(struct ext_code ext_code,
 
 	/* Program alert request */
 	if (alert & CPU_MF_INT_SF_PRA) {
-		if (cpuhw->flags & PMU_F_IN_USE)
+		if (cpuhw->flags & PMU_F_IN_USE) {
 			if (SAMPL_DIAG_MODE(&cpuhw->event->hw))
 				hw_collect_aux(cpuhw);
 			else
 				hw_perf_event_update(cpuhw->event, 0);
-		else
-			WARN_ON_ONCE(!(cpuhw->flags & PMU_F_IN_USE));
+		}
 	}
 
 	/* Report measurement alerts only for non-PRA codes */