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Message-Id: <20220704150514.48816-3-elver@google.com>
Date: Mon, 4 Jul 2022 17:05:02 +0200
From: Marco Elver <elver@...gle.com>
To: elver@...gle.com, Peter Zijlstra <peterz@...radead.org>,
Frederic Weisbecker <frederic@...nel.org>,
Ingo Molnar <mingo@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...hat.com>,
Namhyung Kim <namhyung@...nel.org>,
Dmitry Vyukov <dvyukov@...gle.com>,
Michael Ellerman <mpe@...erman.id.au>,
linuxppc-dev@...ts.ozlabs.org, linux-perf-users@...r.kernel.org,
x86@...nel.org, linux-sh@...r.kernel.org,
kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org
Subject: [PATCH v3 02/14] perf/hw_breakpoint: Provide hw_breakpoint_is_used()
and use in test
Provide hw_breakpoint_is_used() to check if breakpoints are in use on
the system.
Use it in the KUnit test to verify the global state before and after a
test case.
Signed-off-by: Marco Elver <elver@...gle.com>
---
v3:
* New patch.
---
include/linux/hw_breakpoint.h | 3 +++
kernel/events/hw_breakpoint.c | 29 +++++++++++++++++++++++++++++
kernel/events/hw_breakpoint_test.c | 12 +++++++++++-
3 files changed, 43 insertions(+), 1 deletion(-)
diff --git a/include/linux/hw_breakpoint.h b/include/linux/hw_breakpoint.h
index 78dd7035d1e5..a3fb846705eb 100644
--- a/include/linux/hw_breakpoint.h
+++ b/include/linux/hw_breakpoint.h
@@ -74,6 +74,7 @@ register_wide_hw_breakpoint(struct perf_event_attr *attr,
extern int register_perf_hw_breakpoint(struct perf_event *bp);
extern void unregister_hw_breakpoint(struct perf_event *bp);
extern void unregister_wide_hw_breakpoint(struct perf_event * __percpu *cpu_events);
+extern bool hw_breakpoint_is_used(void);
extern int dbg_reserve_bp_slot(struct perf_event *bp);
extern int dbg_release_bp_slot(struct perf_event *bp);
@@ -121,6 +122,8 @@ register_perf_hw_breakpoint(struct perf_event *bp) { return -ENOSYS; }
static inline void unregister_hw_breakpoint(struct perf_event *bp) { }
static inline void
unregister_wide_hw_breakpoint(struct perf_event * __percpu *cpu_events) { }
+static inline bool hw_breakpoint_is_used(void) { return false; }
+
static inline int
reserve_bp_slot(struct perf_event *bp) {return -ENOSYS; }
static inline void release_bp_slot(struct perf_event *bp) { }
diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c
index f32320ac02fd..fd5cd1f9e7fc 100644
--- a/kernel/events/hw_breakpoint.c
+++ b/kernel/events/hw_breakpoint.c
@@ -604,6 +604,35 @@ void unregister_wide_hw_breakpoint(struct perf_event * __percpu *cpu_events)
}
EXPORT_SYMBOL_GPL(unregister_wide_hw_breakpoint);
+/**
+ * hw_breakpoint_is_used - check if breakpoints are currently used
+ *
+ * Returns: true if breakpoints are used, false otherwise.
+ */
+bool hw_breakpoint_is_used(void)
+{
+ int cpu;
+
+ if (!constraints_initialized)
+ return false;
+
+ for_each_possible_cpu(cpu) {
+ for (int type = 0; type < TYPE_MAX; ++type) {
+ struct bp_cpuinfo *info = get_bp_info(cpu, type);
+
+ if (info->cpu_pinned)
+ return true;
+
+ for (int slot = 0; slot < nr_slots[type]; ++slot) {
+ if (info->tsk_pinned[slot])
+ return true;
+ }
+ }
+ }
+
+ return false;
+}
+
static struct notifier_block hw_breakpoint_exceptions_nb = {
.notifier_call = hw_breakpoint_exceptions_notify,
/* we need to be notified first */
diff --git a/kernel/events/hw_breakpoint_test.c b/kernel/events/hw_breakpoint_test.c
index 433c5c45e2a5..5ced822df788 100644
--- a/kernel/events/hw_breakpoint_test.c
+++ b/kernel/events/hw_breakpoint_test.c
@@ -294,7 +294,14 @@ static struct kunit_case hw_breakpoint_test_cases[] = {
static int test_init(struct kunit *test)
{
/* Most test cases want 2 distinct CPUs. */
- return num_online_cpus() < 2 ? -EINVAL : 0;
+ if (num_online_cpus() < 2)
+ return -EINVAL;
+
+ /* Want the system to not use breakpoints elsewhere. */
+ if (hw_breakpoint_is_used())
+ return -EBUSY;
+
+ return 0;
}
static void test_exit(struct kunit *test)
@@ -308,6 +315,9 @@ static void test_exit(struct kunit *test)
kthread_stop(__other_task);
__other_task = NULL;
}
+
+ /* Verify that internal state agrees that no breakpoints are in use. */
+ KUNIT_EXPECT_FALSE(test, hw_breakpoint_is_used());
}
static struct kunit_suite hw_breakpoint_test_suite = {
--
2.37.0.rc0.161.g10f37bed90-goog
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