The following commit has been merged into the perf/core branch of tip:
Commit-ID: c70ca298036c58a88686ff388d3d367e9d21acf0
Gitweb: https://git.kernel.org/tip/c70ca298036c58a88686ff388d3d367e9d21acf0
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Mon, 04 Nov 2024 14:39:13 +01:00
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Tue, 04 Mar 2025 09:42:14 +01:00
perf/core: Simplify the perf_event_alloc() error path
The error cleanup sequence in perf_event_alloc() is a subset of the
existing _free_event() function (it must of course be).
Split this out into __free_event() and simplify the error path.
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Reviewed-by: Ravi Bangoria <ravi.bangoria@xxxxxxx>
Link: https://lore.kernel.org/r/20241104135517.967889521@xxxxxxxxxxxxx
---
include/linux/perf_event.h | 16 ++--
kernel/events/core.c | 138 ++++++++++++++++++------------------
2 files changed, 78 insertions(+), 76 deletions(-)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index c4525ba..8c0117b 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -673,13 +673,15 @@ struct swevent_hlist {
struct rcu_head rcu_head;
};
-#define PERF_ATTACH_CONTEXT 0x01
-#define PERF_ATTACH_GROUP 0x02
-#define PERF_ATTACH_TASK 0x04
-#define PERF_ATTACH_TASK_DATA 0x08
-#define PERF_ATTACH_ITRACE 0x10
-#define PERF_ATTACH_SCHED_CB 0x20
-#define PERF_ATTACH_CHILD 0x40
+#define PERF_ATTACH_CONTEXT 0x0001
+#define PERF_ATTACH_GROUP 0x0002
+#define PERF_ATTACH_TASK 0x0004
+#define PERF_ATTACH_TASK_DATA 0x0008
+#define PERF_ATTACH_ITRACE 0x0010
+#define PERF_ATTACH_SCHED_CB 0x0020
+#define PERF_ATTACH_CHILD 0x0040
+#define PERF_ATTACH_EXCLUSIVE 0x0080
+#define PERF_ATTACH_CALLCHAIN 0x0100
struct bpf_prog;
struct perf_cgroup;
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 6ccf363..1b8b1c8 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5289,6 +5289,8 @@ static int exclusive_event_init(struct perf_event *event)
return -EBUSY;
}
+ event->attach_state |= PERF_ATTACH_EXCLUSIVE;
+
return 0;
}
@@ -5296,14 +5298,13 @@ static void exclusive_event_destroy(struct perf_event *event)
{
struct pmu *pmu = event->pmu;
- if (!is_exclusive_pmu(pmu))
- return;
-
/* see comment in exclusive_event_init() */
if (event->attach_state & PERF_ATTACH_TASK)
atomic_dec(&pmu->exclusive_cnt);
else
atomic_inc(&pmu->exclusive_cnt);
+
+ event->attach_state &= ~PERF_ATTACH_EXCLUSIVE;
}
static bool exclusive_event_match(struct perf_event *e1, struct perf_event *e2)
@@ -5362,40 +5363,20 @@ static void perf_pending_task_sync(struct perf_event *event)
rcuwait_wait_event(&event->pending_work_wait, !event->pending_work, TASK_UNINTERRUPTIBLE);
}
-static void _free_event(struct perf_event *event)
+/* vs perf_event_alloc() error */
+static void __free_event(struct perf_event *event)
{
- irq_work_sync(&event->pending_irq);
- irq_work_sync(&event->pending_disable_irq);
- perf_pending_task_sync(event);
+ if (event->attach_state & PERF_ATTACH_CALLCHAIN)
+ put_callchain_buffers();
- unaccount_event(event);
+ kfree(event->addr_filter_ranges);
- security_perf_event_free(event);
-
- if (event->rb) {
- /*
- * Can happen when we close an event with re-directed output.
- *
- * Since we have a 0 refcount, perf_mmap_close() will skip
- * over us; possibly making our ring_buffer_put() the last.
- */
- mutex_lock(&event->mmap_mutex);
- ring_buffer_attach(event, NULL);
- mutex_unlock(&event->mmap_mutex);
- }
+ if (event->attach_state & PERF_ATTACH_EXCLUSIVE)
+ exclusive_event_destroy(event);
if (is_cgroup_event(event))
perf_detach_cgroup(event);
- if (!event->parent) {
- if (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN)
- put_callchain_buffers();
- }
-
- perf_event_free_bpf_prog(event);
- perf_addr_filters_splice(event, NULL);
- kfree(event->addr_filter_ranges);
-
if (event->destroy)
event->destroy(event);
@@ -5406,22 +5387,58 @@ static void _free_event(struct perf_event *event)
if (event->hw.target)
put_task_struct(event->hw.target);
- if (event->pmu_ctx)
+ if (event->pmu_ctx) {
+ /*
+ * put_pmu_ctx() needs an event->ctx reference, because of
+ * epc->ctx.
+ */
+ WARN_ON_ONCE(!event->ctx);
+ WARN_ON_ONCE(event->pmu_ctx->ctx != event->ctx);
put_pmu_ctx(event->pmu_ctx);
+ }
/*
- * perf_event_free_task() relies on put_ctx() being 'last', in particular
- * all task references must be cleaned up.
+ * perf_event_free_task() relies on put_ctx() being 'last', in
+ * particular all task references must be cleaned up.
*/
if (event->ctx)
put_ctx(event->ctx);
- exclusive_event_destroy(event);
- module_put(event->pmu->module);
+ if (event->pmu)
+ module_put(event->pmu->module);
call_rcu(&event->rcu_head, free_event_rcu);
}
+/* vs perf_event_alloc() success */
+static void _free_event(struct perf_event *event)
+{
+ irq_work_sync(&event->pending_irq);
+ irq_work_sync(&event->pending_disable_irq);
+ perf_pending_task_sync(event);
+
+ unaccount_event(event);
+
+ security_perf_event_free(event);
+
+ if (event->rb) {
+ /*
+ * Can happen when we close an event with re-directed output.
+ *
+ * Since we have a 0 refcount, perf_mmap_close() will skip
+ * over us; possibly making our ring_buffer_put() the last.
+ */
+ mutex_lock(&event->mmap_mutex);
+ ring_buffer_attach(event, NULL);
+ mutex_unlock(&event->mmap_mutex);
+ }
+
+ perf_event_free_bpf_prog(event);
+ perf_addr_filters_splice(event, NULL);
+
+ __free_event(event);
+}
+
/*
* Used to free events which have a known refcount of 1, such as in error paths
* where the event isn't exposed yet and inherited events.
@@ -12093,8 +12110,10 @@ static int perf_try_init_event(struct pmu *pmu, struct perf_event *event)
event->destroy(event);
}
- if (ret)
+ if (ret) {
+ event->pmu = NULL;
module_put(pmu->module);
+ }
return ret;
}
@@ -12422,7 +12441,7 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
* See perf_output_read().
*/
if (has_inherit_and_sample_read(attr) && !(attr->sample_type & PERF_SAMPLE_TID))
- goto err_ns;
+ goto err;
if (!has_branch_stack(event))
event->attr.branch_sample_type = 0;
@@ -12430,7 +12449,7 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
pmu = perf_init_event(event);
if (IS_ERR(pmu)) {
err = PTR_ERR(pmu);
- goto err_ns;
+ goto err;
}
/*
@@ -12440,25 +12459,25 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
*/
if (pmu->task_ctx_nr == perf_invalid_context && (task || cgroup_fd != -1)) {
err = -EINVAL;
- goto err_pmu;
+ goto err;
}
if (event->attr.aux_output &&
(!(pmu->capabilities & PERF_PMU_CAP_AUX_OUTPUT) ||
event->attr.aux_pause || event->attr.aux_resume)) {
err = -EOPNOTSUPP;
- goto err_pmu;
+ goto err;
}
if (event->attr.aux_pause && event->attr.aux_resume) {
err = -EINVAL;
- goto err_pmu;
+ goto err;
}
if (event->attr.aux_start_paused) {
if (!(pmu->capabilities & PERF_PMU_CAP_AUX_PAUSE)) {
err = -EOPNOTSUPP;
- goto err_pmu;
+ goto err;
}
event->hw.aux_paused = 1;
}
@@ -12466,12 +12485,12 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
if (cgroup_fd != -1) {
err = perf_cgroup_connect(cgroup_fd, event, attr, group_leader);
if (err)
- goto err_pmu;
+ goto err;
}
err = exclusive_event_init(event);
if (err)
- goto err_pmu;
+ goto err;
if (has_addr_filter(event)) {
event->addr_filter_ranges = kcalloc(pmu->nr_addr_filters,
@@ -12479,7 +12498,7 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
GFP_KERNEL);
if (!event->addr_filter_ranges) {
err = -ENOMEM;
- goto err_per_task;
+ goto err;
}
/*
@@ -12504,41 +12523,22 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
if (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN) {
err = get_callchain_buffers(attr->sample_max_stack);
if (err)
- goto err_addr_filters;
+ goto err;
+ event->attach_state |= PERF_ATTACH_CALLCHAIN;
}
}
err = security_perf_event_alloc(event);
if (err)
- goto err_callchain_buffer;
+ goto err;
/* symmetric to unaccount_event() in _free_event() */
account_event(event);
return event;
-err_callchain_buffer:
- if (!event->parent) {
- if (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN)
- put_callchain_buffers();
- }
-err_addr_filters:
- kfree(event->addr_filter_ranges);
-
-err_per_task:
- exclusive_event_destroy(event);
-
-err_pmu:
- if (is_cgroup_event(event))
- perf_detach_cgroup(event);
- if (event->destroy)
- event->destroy(event);
- module_put(pmu->module);
-err_ns:
- if (event->hw.target)
- put_task_struct(event->hw.target);
- call_rcu(&event->rcu_head, free_event_rcu);
-
+err:
+ __free_event(event);
return ERR_PTR(err);
}
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