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Date:   Tue, 24 Oct 2023 15:23:04 -0700
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Subject: [PATCH v3 01/50] perf rwsem: Add debug mode that uses a mutex
From:   Ian Rogers <irogers@google.com>
To:     Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Ian Rogers <irogers@google.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Nick Terrell <terrelln@fb.com>,
        Kan Liang <kan.liang@linux.intel.com>,
        Andi Kleen <ak@linux.intel.com>, Leo Yan <leo.yan@linaro.org>,
        Song Liu <song@kernel.org>,
        Sandipan Das <sandipan.das@amd.com>,
        James Clark <james.clark@arm.com>,
        Anshuman Khandual <anshuman.khandual@arm.com>,
        Miguel Ojeda <ojeda@kernel.org>,
        Liam Howlett <liam.howlett@oracle.com>,
        Yang Jihong <yangjihong1@huawei.com>,
        Athira Rajeev <atrajeev@linux.vnet.ibm.com>,
        Kajol Jain <kjain@linux.ibm.com>,
        K Prateek Nayak <kprateek.nayak@amd.com>,
        Sean Christopherson <seanjc@google.com>,
        Yanteng Si <siyanteng@loongson.cn>,
        Ravi Bangoria <ravi.bangoria@amd.com>,
        German Gomez <german.gomez@arm.com>,
        Changbin Du <changbin.du@huawei.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        liuwenyu <liuwenyu7@huawei.com>, linux-kernel@vger.kernel.org,
        linux-perf-users@vger.kernel.org
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Precedence: bulk

Mutex error check will capture trying to take the lock recursively and
other problems that rwlock won't. At the expense of concurrency, adda
debug mode that uses a mutex in place of a rwsem.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/rwsem.c | 34 ++++++++++++++++++++++++++++++++++
 tools/perf/util/rwsem.h | 11 +++++++++++
 2 files changed, 45 insertions(+)

diff --git a/tools/perf/util/rwsem.c b/tools/perf/util/rwsem.c
index f3d29d8ddc99..5109167f27f7 100644
--- a/tools/perf/util/rwsem.c
+++ b/tools/perf/util/rwsem.c
@@ -2,32 +2,66 @@
 #include "util.h"
 #include "rwsem.h"
 
+#if RWS_ERRORCHECK
+#include "mutex.h"
+#endif
+
 int init_rwsem(struct rw_semaphore *sem)
 {
+#if RWS_ERRORCHECK
+	mutex_init(&sem->mtx);
+	return 0;
+#else
 	return pthread_rwlock_init(&sem->lock, NULL);
+#endif
 }
 
 int exit_rwsem(struct rw_semaphore *sem)
 {
+#if RWS_ERRORCHECK
+	mutex_destroy(&sem->mtx);
+	return 0;
+#else
 	return pthread_rwlock_destroy(&sem->lock);
+#endif
 }
 
 int down_read(struct rw_semaphore *sem)
 {
+#if RWS_ERRORCHECK
+	mutex_lock(&sem->mtx);
+	return 0;
+#else
 	return perf_singlethreaded ? 0 : pthread_rwlock_rdlock(&sem->lock);
+#endif
 }
 
 int up_read(struct rw_semaphore *sem)
 {
+#if RWS_ERRORCHECK
+	mutex_unlock(&sem->mtx);
+	return 0;
+#else
 	return perf_singlethreaded ? 0 : pthread_rwlock_unlock(&sem->lock);
+#endif
 }
 
 int down_write(struct rw_semaphore *sem)
 {
+#if RWS_ERRORCHECK
+	mutex_lock(&sem->mtx);
+	return 0;
+#else
 	return perf_singlethreaded ? 0 : pthread_rwlock_wrlock(&sem->lock);
+#endif
 }
 
 int up_write(struct rw_semaphore *sem)
 {
+#if RWS_ERRORCHECK
+	mutex_unlock(&sem->mtx);
+	return 0;
+#else
 	return perf_singlethreaded ? 0 : pthread_rwlock_unlock(&sem->lock);
+#endif
 }
diff --git a/tools/perf/util/rwsem.h b/tools/perf/util/rwsem.h
index 94565ad4d494..ef5cbc31d967 100644
--- a/tools/perf/util/rwsem.h
+++ b/tools/perf/util/rwsem.h
@@ -2,9 +2,20 @@
 #define _PERF_RWSEM_H
 
 #include <pthread.h>
+#include "mutex.h"
+
+/*
+ * Mutexes have additional error checking. Enable to use a mutex rather than a
+ * rwlock for debugging.
+ */
+#define RWS_ERRORCHECK 0
 
 struct rw_semaphore {
+#if RWS_ERRORCHECK
+	struct mutex mtx;
+#else
 	pthread_rwlock_t lock;
+#endif
 };
 
 int init_rwsem(struct rw_semaphore *sem);
-- 
2.42.0.758.gaed0368e0e-goog