From: Marco Elver <elver@google.com>
To: elver@google.com, Peter Zijlstra <peterz@infradead.org>,
Frederic Weisbecker <frederic@kernel.org>,
Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
Dmitry Vyukov <dvyukov@google.com>,
Michael Ellerman <mpe@ellerman.id.au>,
linuxppc-dev@lists.ozlabs.org, linux-perf-users@vger.kernel.org,
x86@kernel.org, linux-sh@vger.kernel.org,
kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org
Subject: [PATCH v2 08/13] powerpc/hw_breakpoint: Avoid relying on caller synchronization
Date: Tue, 28 Jun 2022 11:58:28 +0200 [thread overview]
Message-ID: <20220628095833.2579903-9-elver@google.com> (raw)
In-Reply-To: <20220628095833.2579903-1-elver@google.com>
Internal data structures (cpu_bps, task_bps) of powerpc's hw_breakpoint
implementation have relied on nr_bp_mutex serializing access to them.
Before overhauling synchronization of kernel/events/hw_breakpoint.c,
introduce 2 spinlocks to synchronize cpu_bps and task_bps respectively,
thus avoiding reliance on callers synchronizing powerpc's hw_breakpoint.
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Marco Elver <elver@google.com>
---
v2:
* New patch.
---
arch/powerpc/kernel/hw_breakpoint.c | 53 ++++++++++++++++++++++-------
1 file changed, 40 insertions(+), 13 deletions(-)
diff --git a/arch/powerpc/kernel/hw_breakpoint.c b/arch/powerpc/kernel/hw_breakpoint.c
index 2669f80b3a49..8db1a15d7acb 100644
--- a/arch/powerpc/kernel/hw_breakpoint.c
+++ b/arch/powerpc/kernel/hw_breakpoint.c
@@ -15,6 +15,7 @@
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/smp.h>
+#include <linux/spinlock.h>
#include <linux/debugfs.h>
#include <linux/init.h>
@@ -129,7 +130,14 @@ struct breakpoint {
bool ptrace_bp;
};
+/*
+ * While kernel/events/hw_breakpoint.c does its own synchronization, we cannot
+ * rely on it safely synchronizing internals here; however, we can rely on it
+ * not requesting more breakpoints than available.
+ */
+static DEFINE_SPINLOCK(cpu_bps_lock);
static DEFINE_PER_CPU(struct breakpoint *, cpu_bps[HBP_NUM_MAX]);
+static DEFINE_SPINLOCK(task_bps_lock);
static LIST_HEAD(task_bps);
static struct breakpoint *alloc_breakpoint(struct perf_event *bp)
@@ -174,7 +182,9 @@ static int task_bps_add(struct perf_event *bp)
if (IS_ERR(tmp))
return PTR_ERR(tmp);
+ spin_lock(&task_bps_lock);
list_add(&tmp->list, &task_bps);
+ spin_unlock(&task_bps_lock);
return 0;
}
@@ -182,6 +192,7 @@ static void task_bps_remove(struct perf_event *bp)
{
struct list_head *pos, *q;
+ spin_lock(&task_bps_lock);
list_for_each_safe(pos, q, &task_bps) {
struct breakpoint *tmp = list_entry(pos, struct breakpoint, list);
@@ -191,6 +202,7 @@ static void task_bps_remove(struct perf_event *bp)
break;
}
}
+ spin_unlock(&task_bps_lock);
}
/*
@@ -200,12 +212,17 @@ static void task_bps_remove(struct perf_event *bp)
static bool all_task_bps_check(struct perf_event *bp)
{
struct breakpoint *tmp;
+ bool ret = false;
+ spin_lock(&task_bps_lock);
list_for_each_entry(tmp, &task_bps, list) {
- if (!can_co_exist(tmp, bp))
- return true;
+ if (!can_co_exist(tmp, bp)) {
+ ret = true;
+ break;
+ }
}
- return false;
+ spin_unlock(&task_bps_lock);
+ return ret;
}
/*
@@ -215,13 +232,18 @@ static bool all_task_bps_check(struct perf_event *bp)
static bool same_task_bps_check(struct perf_event *bp)
{
struct breakpoint *tmp;
+ bool ret = false;
+ spin_lock(&task_bps_lock);
list_for_each_entry(tmp, &task_bps, list) {
if (tmp->bp->hw.target == bp->hw.target &&
- !can_co_exist(tmp, bp))
- return true;
+ !can_co_exist(tmp, bp)) {
+ ret = true;
+ break;
+ }
}
- return false;
+ spin_unlock(&task_bps_lock);
+ return ret;
}
static int cpu_bps_add(struct perf_event *bp)
@@ -234,6 +256,7 @@ static int cpu_bps_add(struct perf_event *bp)
if (IS_ERR(tmp))
return PTR_ERR(tmp);
+ spin_lock(&cpu_bps_lock);
cpu_bp = per_cpu_ptr(cpu_bps, bp->cpu);
for (i = 0; i < nr_wp_slots(); i++) {
if (!cpu_bp[i]) {
@@ -241,6 +264,7 @@ static int cpu_bps_add(struct perf_event *bp)
break;
}
}
+ spin_unlock(&cpu_bps_lock);
return 0;
}
@@ -249,6 +273,7 @@ static void cpu_bps_remove(struct perf_event *bp)
struct breakpoint **cpu_bp;
int i = 0;
+ spin_lock(&cpu_bps_lock);
cpu_bp = per_cpu_ptr(cpu_bps, bp->cpu);
for (i = 0; i < nr_wp_slots(); i++) {
if (!cpu_bp[i])
@@ -260,19 +285,25 @@ static void cpu_bps_remove(struct perf_event *bp)
break;
}
}
+ spin_unlock(&cpu_bps_lock);
}
static bool cpu_bps_check(int cpu, struct perf_event *bp)
{
struct breakpoint **cpu_bp;
+ bool ret = false;
int i;
+ spin_lock(&cpu_bps_lock);
cpu_bp = per_cpu_ptr(cpu_bps, cpu);
for (i = 0; i < nr_wp_slots(); i++) {
- if (cpu_bp[i] && !can_co_exist(cpu_bp[i], bp))
- return true;
+ if (cpu_bp[i] && !can_co_exist(cpu_bp[i], bp)) {
+ ret = true;
+ break;
+ }
}
- return false;
+ spin_unlock(&cpu_bps_lock);
+ return ret;
}
static bool all_cpu_bps_check(struct perf_event *bp)
@@ -286,10 +317,6 @@ static bool all_cpu_bps_check(struct perf_event *bp)
return false;
}
-/*
- * We don't use any locks to serialize accesses to cpu_bps or task_bps
- * because are already inside nr_bp_mutex.
- */
int arch_reserve_bp_slot(struct perf_event *bp)
{
int ret;
--
2.37.0.rc0.161.g10f37bed90-goog
next prev parent reply other threads:[~2022-06-28 10:00 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-28 9:58 [PATCH v2 00/13] perf/hw_breakpoint: Optimize for thousands of tasks Marco Elver
2022-06-28 9:58 ` [PATCH v2 01/13] perf/hw_breakpoint: Add KUnit test for constraints accounting Marco Elver
2022-06-28 12:53 ` Dmitry Vyukov
2022-06-28 13:26 ` Marco Elver
2022-06-28 9:58 ` [PATCH v2 02/13] perf/hw_breakpoint: Clean up headers Marco Elver
2022-06-28 9:58 ` [PATCH v2 03/13] perf/hw_breakpoint: Optimize list of per-task breakpoints Marco Elver
2022-06-28 13:08 ` Dmitry Vyukov
2022-06-28 14:53 ` Marco Elver
2022-06-28 15:27 ` Dmitry Vyukov
2022-06-28 9:58 ` [PATCH v2 04/13] perf/hw_breakpoint: Mark data __ro_after_init Marco Elver
2022-06-28 9:58 ` [PATCH v2 05/13] perf/hw_breakpoint: Optimize constant number of breakpoint slots Marco Elver
2022-06-28 9:58 ` [PATCH v2 06/13] perf/hw_breakpoint: Make hw_breakpoint_weight() inlinable Marco Elver
2022-06-28 13:16 ` Dmitry Vyukov
2022-06-28 9:58 ` [PATCH v2 07/13] perf/hw_breakpoint: Remove useless code related to flexible breakpoints Marco Elver
2022-06-28 13:18 ` Dmitry Vyukov
2022-06-28 9:58 ` Marco Elver [this message]
2022-06-28 13:21 ` [PATCH v2 08/13] powerpc/hw_breakpoint: Avoid relying on caller synchronization Dmitry Vyukov
2022-07-01 8:54 ` Christophe Leroy
2022-07-01 9:41 ` Marco Elver
2022-07-01 10:15 ` Christophe Leroy
2022-06-28 9:58 ` [PATCH v2 09/13] locking/percpu-rwsem: Add percpu_is_write_locked() and percpu_is_read_locked() Marco Elver
2022-06-28 14:44 ` Dmitry Vyukov
2022-06-28 9:58 ` [PATCH v2 10/13] perf/hw_breakpoint: Reduce contention with large number of tasks Marco Elver
2022-06-28 14:45 ` Dmitry Vyukov
2022-06-28 9:58 ` [PATCH v2 11/13] perf/hw_breakpoint: Introduce bp_slots_histogram Marco Elver
2022-06-28 14:52 ` Dmitry Vyukov
2022-06-28 9:58 ` [PATCH v2 12/13] perf/hw_breakpoint: Optimize max_bp_pinned_slots() for CPU-independent task targets Marco Elver
2022-06-28 15:41 ` Dmitry Vyukov
2022-06-28 9:58 ` [PATCH v2 13/13] perf/hw_breakpoint: Optimize toggle_bp_slot() " Marco Elver
2022-06-28 10:54 ` Marco Elver
2022-06-28 15:45 ` Dmitry Vyukov
2022-06-28 16:00 ` Marco Elver
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