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Diffstat (limited to 'kernel/events/core.c')
-rw-r--r--kernel/events/core.c473
1 files changed, 250 insertions, 223 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 6b41c1899a8b..b391907d5352 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -196,9 +196,6 @@ static void cpu_ctx_sched_in(struct perf_cpu_context *cpuctx,
static void update_context_time(struct perf_event_context *ctx);
static u64 perf_event_time(struct perf_event *event);
-static void ring_buffer_attach(struct perf_event *event,
- struct ring_buffer *rb);
-
void __weak perf_event_print_debug(void) { }
extern __weak const char *perf_pmu_name(void)
@@ -2918,6 +2915,7 @@ static void free_event_rcu(struct rcu_head *head)
}
static void ring_buffer_put(struct ring_buffer *rb);
+static void ring_buffer_detach(struct perf_event *event, struct ring_buffer *rb);
static void free_event(struct perf_event *event)
{
@@ -2942,15 +2940,30 @@ static void free_event(struct perf_event *event)
if (has_branch_stack(event)) {
static_key_slow_dec_deferred(&perf_sched_events);
/* is system-wide event */
- if (!(event->attach_state & PERF_ATTACH_TASK))
+ if (!(event->attach_state & PERF_ATTACH_TASK)) {
atomic_dec(&per_cpu(perf_branch_stack_events,
event->cpu));
+ }
}
}
if (event->rb) {
- ring_buffer_put(event->rb);
- event->rb = NULL;
+ struct ring_buffer *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);
+ rb = event->rb;
+ if (rb) {
+ rcu_assign_pointer(event->rb, NULL);
+ ring_buffer_detach(event, rb);
+ ring_buffer_put(rb); /* could be last */
+ }
+ mutex_unlock(&event->mmap_mutex);
}
if (is_cgroup_event(event))
@@ -3188,30 +3201,13 @@ static unsigned int perf_poll(struct file *file, poll_table *wait)
unsigned int events = POLL_HUP;
/*
- * Race between perf_event_set_output() and perf_poll(): perf_poll()
- * grabs the rb reference but perf_event_set_output() overrides it.
- * Here is the timeline for two threads T1, T2:
- * t0: T1, rb = rcu_dereference(event->rb)
- * t1: T2, old_rb = event->rb
- * t2: T2, event->rb = new rb
- * t3: T2, ring_buffer_detach(old_rb)
- * t4: T1, ring_buffer_attach(rb1)
- * t5: T1, poll_wait(event->waitq)
- *
- * To avoid this problem, we grab mmap_mutex in perf_poll()
- * thereby ensuring that the assignment of the new ring buffer
- * and the detachment of the old buffer appear atomic to perf_poll()
+ * Pin the event->rb by taking event->mmap_mutex; otherwise
+ * perf_event_set_output() can swizzle our rb and make us miss wakeups.
*/
mutex_lock(&event->mmap_mutex);
-
- rcu_read_lock();
- rb = rcu_dereference(event->rb);
- if (rb) {
- ring_buffer_attach(event, rb);
+ rb = event->rb;
+ if (rb)
events = atomic_xchg(&rb->poll, 0);
- }
- rcu_read_unlock();
-
mutex_unlock(&event->mmap_mutex);
poll_wait(file, &event->waitq, wait);
@@ -3521,16 +3517,12 @@ static void ring_buffer_attach(struct perf_event *event,
return;
spin_lock_irqsave(&rb->event_lock, flags);
- if (!list_empty(&event->rb_entry))
- goto unlock;
-
- list_add(&event->rb_entry, &rb->event_list);
-unlock:
+ if (list_empty(&event->rb_entry))
+ list_add(&event->rb_entry, &rb->event_list);
spin_unlock_irqrestore(&rb->event_lock, flags);
}
-static void ring_buffer_detach(struct perf_event *event,
- struct ring_buffer *rb)
+static void ring_buffer_detach(struct perf_event *event, struct ring_buffer *rb)
{
unsigned long flags;
@@ -3549,13 +3541,10 @@ static void ring_buffer_wakeup(struct perf_event *event)
rcu_read_lock();
rb = rcu_dereference(event->rb);
- if (!rb)
- goto unlock;
-
- list_for_each_entry_rcu(event, &rb->event_list, rb_entry)
- wake_up_all(&event->waitq);
-
-unlock:
+ if (rb) {
+ list_for_each_entry_rcu(event, &rb->event_list, rb_entry)
+ wake_up_all(&event->waitq);
+ }
rcu_read_unlock();
}
@@ -3584,18 +3573,10 @@ static struct ring_buffer *ring_buffer_get(struct perf_event *event)
static void ring_buffer_put(struct ring_buffer *rb)
{
- struct perf_event *event, *n;
- unsigned long flags;
-
if (!atomic_dec_and_test(&rb->refcount))
return;
- spin_lock_irqsave(&rb->event_lock, flags);
- list_for_each_entry_safe(event, n, &rb->event_list, rb_entry) {
- list_del_init(&event->rb_entry);
- wake_up_all(&event->waitq);
- }
- spin_unlock_irqrestore(&rb->event_lock, flags);
+ WARN_ON_ONCE(!list_empty(&rb->event_list));
call_rcu(&rb->rcu_head, rb_free_rcu);
}
@@ -3605,26 +3586,100 @@ static void perf_mmap_open(struct vm_area_struct *vma)
struct perf_event *event = vma->vm_file->private_data;
atomic_inc(&event->mmap_count);
+ atomic_inc(&event->rb->mmap_count);
}
+/*
+ * A buffer can be mmap()ed multiple times; either directly through the same
+ * event, or through other events by use of perf_event_set_output().
+ *
+ * In order to undo the VM accounting done by perf_mmap() we need to destroy
+ * the buffer here, where we still have a VM context. This means we need
+ * to detach all events redirecting to us.
+ */
static void perf_mmap_close(struct vm_area_struct *vma)
{
struct perf_event *event = vma->vm_file->private_data;
- if (atomic_dec_and_mutex_lock(&event->mmap_count, &event->mmap_mutex)) {
- unsigned long size = perf_data_size(event->rb);
- struct user_struct *user = event->mmap_user;
- struct ring_buffer *rb = event->rb;
+ struct ring_buffer *rb = event->rb;
+ struct user_struct *mmap_user = rb->mmap_user;
+ int mmap_locked = rb->mmap_locked;
+ unsigned long size = perf_data_size(rb);
+
+ atomic_dec(&rb->mmap_count);
+
+ if (!atomic_dec_and_mutex_lock(&event->mmap_count, &event->mmap_mutex))
+ return;
+
+ /* Detach current event from the buffer. */
+ rcu_assign_pointer(event->rb, NULL);
+ ring_buffer_detach(event, rb);
+ mutex_unlock(&event->mmap_mutex);
- atomic_long_sub((size >> PAGE_SHIFT) + 1, &user->locked_vm);
- vma->vm_mm->pinned_vm -= event->mmap_locked;
- rcu_assign_pointer(event->rb, NULL);
- ring_buffer_detach(event, rb);
+ /* If there's still other mmap()s of this buffer, we're done. */
+ if (atomic_read(&rb->mmap_count)) {
+ ring_buffer_put(rb); /* can't be last */
+ return;
+ }
+
+ /*
+ * No other mmap()s, detach from all other events that might redirect
+ * into the now unreachable buffer. Somewhat complicated by the
+ * fact that rb::event_lock otherwise nests inside mmap_mutex.
+ */
+again:
+ rcu_read_lock();
+ list_for_each_entry_rcu(event, &rb->event_list, rb_entry) {
+ if (!atomic_long_inc_not_zero(&event->refcount)) {
+ /*
+ * This event is en-route to free_event() which will
+ * detach it and remove it from the list.
+ */
+ continue;
+ }
+ rcu_read_unlock();
+
+ mutex_lock(&event->mmap_mutex);
+ /*
+ * Check we didn't race with perf_event_set_output() which can
+ * swizzle the rb from under us while we were waiting to
+ * acquire mmap_mutex.
+ *
+ * If we find a different rb; ignore this event, a next
+ * iteration will no longer find it on the list. We have to
+ * still restart the iteration to make sure we're not now
+ * iterating the wrong list.
+ */
+ if (event->rb == rb) {
+ rcu_assign_pointer(event->rb, NULL);
+ ring_buffer_detach(event, rb);
+ ring_buffer_put(rb); /* can't be last, we still have one */
+ }
mutex_unlock(&event->mmap_mutex);
+ put_event(event);
- ring_buffer_put(rb);
- free_uid(user);
+ /*
+ * Restart the iteration; either we're on the wrong list or
+ * destroyed its integrity by doing a deletion.
+ */
+ goto again;
}
+ rcu_read_unlock();
+
+ /*
+ * It could be there's still a few 0-ref events on the list; they'll
+ * get cleaned up by free_event() -- they'll also still have their
+ * ref on the rb and will free it whenever they are done with it.
+ *
+ * Aside from that, this buffer is 'fully' detached and unmapped,
+ * undo the VM accounting.
+ */
+
+ atomic_long_sub((size >> PAGE_SHIFT) + 1, &mmap_user->locked_vm);
+ vma->vm_mm->pinned_vm -= mmap_locked;
+ free_uid(mmap_user);
+
+ ring_buffer_put(rb); /* could be last */
}
static const struct vm_operations_struct perf_mmap_vmops = {
@@ -3674,12 +3729,24 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
return -EINVAL;
WARN_ON_ONCE(event->ctx->parent_ctx);
+again:
mutex_lock(&event->mmap_mutex);
if (event->rb) {
- if (event->rb->nr_pages == nr_pages)
- atomic_inc(&event->rb->refcount);
- else
+ if (event->rb->nr_pages != nr_pages) {
ret = -EINVAL;
+ goto unlock;
+ }
+
+ if (!atomic_inc_not_zero(&event->rb->mmap_count)) {
+ /*
+ * Raced against perf_mmap_close() through
+ * perf_event_set_output(). Try again, hope for better
+ * luck.
+ */
+ mutex_unlock(&event->mmap_mutex);
+ goto again;
+ }
+
goto unlock;
}
@@ -3720,12 +3787,16 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
ret = -ENOMEM;
goto unlock;
}
- rcu_assign_pointer(event->rb, rb);
+
+ atomic_set(&rb->mmap_count, 1);
+ rb->mmap_locked = extra;
+ rb->mmap_user = get_current_user();
atomic_long_add(user_extra, &user->locked_vm);
- event->mmap_locked = extra;
- event->mmap_user = get_current_user();
- vma->vm_mm->pinned_vm += event->mmap_locked;
+ vma->vm_mm->pinned_vm += extra;
+
+ ring_buffer_attach(event, rb);
+ rcu_assign_pointer(event->rb, rb);
perf_event_update_userpage(event);
@@ -3734,7 +3805,11 @@ unlock:
atomic_inc(&event->mmap_count);
mutex_unlock(&event->mmap_mutex);
- vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
+ /*
+ * Since pinned accounting is per vm we cannot allow fork() to copy our
+ * vma.
+ */
+ vma->vm_flags |= VM_DONTCOPY | VM_DONTEXPAND | VM_DONTDUMP;
vma->vm_ops = &perf_mmap_vmops;
return ret;
@@ -4394,6 +4469,64 @@ perf_event_read_event(struct perf_event *event,
perf_output_end(&handle);
}
+typedef int (perf_event_aux_match_cb)(struct perf_event *event, void *data);
+typedef void (perf_event_aux_output_cb)(struct perf_event *event, void *data);
+
+static void
+perf_event_aux_ctx(struct perf_event_context *ctx,
+ perf_event_aux_match_cb match,
+ perf_event_aux_output_cb output,
+ void *data)
+{
+ struct perf_event *event;
+
+ list_for_each_entry_rcu(event, &ctx->event_list, event_entry) {
+ if (event->state < PERF_EVENT_STATE_INACTIVE)
+ continue;
+ if (!event_filter_match(event))
+ continue;
+ if (match(event, data))
+ output(event, data);
+ }
+}
+
+static void
+perf_event_aux(perf_event_aux_match_cb match,
+ perf_event_aux_output_cb output,
+ void *data,
+ struct perf_event_context *task_ctx)
+{
+ struct perf_cpu_context *cpuctx;
+ struct perf_event_context *ctx;
+ struct pmu *pmu;
+ int ctxn;
+
+ rcu_read_lock();
+ list_for_each_entry_rcu(pmu, &pmus, entry) {
+ cpuctx = get_cpu_ptr(pmu->pmu_cpu_context);
+ if (cpuctx->unique_pmu != pmu)
+ goto next;
+ perf_event_aux_ctx(&cpuctx->ctx, match, output, data);
+ if (task_ctx)
+ goto next;
+ ctxn = pmu->task_ctx_nr;
+ if (ctxn < 0)
+ goto next;
+ ctx = rcu_dereference(current->perf_event_ctxp[ctxn]);
+ if (ctx)
+ perf_event_aux_ctx(ctx, match, output, data);
+next:
+ put_cpu_ptr(pmu->pmu_cpu_context);
+ }
+
+ if (task_ctx) {
+ preempt_disable();
+ perf_event_aux_ctx(task_ctx, match, output, data);
+ preempt_enable();
+ }
+ rcu_read_unlock();
+}
+
/*
* task tracking -- fork/exit
*
@@ -4416,8 +4549,9 @@ struct perf_task_event {
};
static void perf_event_task_output(struct perf_event *event,
- struct perf_task_event *task_event)
+ void *data)
{
+ struct perf_task_event *task_event = data;
struct perf_output_handle handle;
struct perf_sample_data sample;
struct task_struct *task = task_event->task;
@@ -4445,62 +4579,11 @@ out:
task_event->event_id.header.size = size;
}
-static int perf_event_task_match(struct perf_event *event)
-{
- if (event->state < PERF_EVENT_STATE_INACTIVE)
- return 0;
-
- if (!event_filter_match(event))
- return 0;
-
- if (event->attr.comm || event->attr.mmap ||
- event->attr.mmap_data || event->attr.task)
- return 1;
-
- return 0;
-}
-
-static void perf_event_task_ctx(struct perf_event_context *ctx,
- struct perf_task_event *task_event)
+static int perf_event_task_match(struct perf_event *event,
+ void *data __maybe_unused)
{
- struct perf_event *event;
-
- list_for_each_entry_rcu(event, &ctx->event_list, event_entry) {
- if (perf_event_task_match(event))
- perf_event_task_output(event, task_event);
- }
-}
-
-static void perf_event_task_event(struct perf_task_event *task_event)
-{
- struct perf_cpu_context *cpuctx;
- struct perf_event_context *ctx;
- struct pmu *pmu;
- int ctxn;
-
- rcu_read_lock();
- list_for_each_entry_rcu(pmu, &pmus, entry) {
- cpuctx = get_cpu_ptr(pmu->pmu_cpu_context);
- if (cpuctx->unique_pmu != pmu)
- goto next;
- perf_event_task_ctx(&cpuctx->ctx, task_event);
-
- ctx = task_event->task_ctx;
- if (!ctx) {
- ctxn = pmu->task_ctx_nr;
- if (ctxn < 0)
- goto next;
- ctx = rcu_dereference(current->perf_event_ctxp[ctxn]);
- if (ctx)
- perf_event_task_ctx(ctx, task_event);
- }
-next:
- put_cpu_ptr(pmu->pmu_cpu_context);
- }
- if (task_event->task_ctx)
- perf_event_task_ctx(task_event->task_ctx, task_event);
-
- rcu_read_unlock();
+ return event->attr.comm || event->attr.mmap ||
+ event->attr.mmap_data || event->attr.task;
}
static void perf_event_task(struct task_struct *task,
@@ -4531,7 +4614,10 @@ static void perf_event_task(struct task_struct *task,
},
};
- perf_event_task_event(&task_event);
+ perf_event_aux(perf_event_task_match,
+ perf_event_task_output,
+ &task_event,
+ task_ctx);
}
void perf_event_fork(struct task_struct *task)
@@ -4557,8 +4643,9 @@ struct perf_comm_event {
};
static void perf_event_comm_output(struct perf_event *event,
- struct perf_comm_event *comm_event)
+ void *data)
{
+ struct perf_comm_event *comm_event = data;
struct perf_output_handle handle;
struct perf_sample_data sample;
int size = comm_event->event_id.header.size;
@@ -4585,39 +4672,16 @@ out:
comm_event->event_id.header.size = size;
}
-static int perf_event_comm_match(struct perf_event *event)
+static int perf_event_comm_match(struct perf_event *event,
+ void *data __maybe_unused)
{
- if (event->state < PERF_EVENT_STATE_INACTIVE)
- return 0;
-
- if (!event_filter_match(event))
- return 0;
-
- if (event->attr.comm)
- return 1;
-
- return 0;
-}
-
-static void perf_event_comm_ctx(struct perf_event_context *ctx,
- struct perf_comm_event *comm_event)
-{
- struct perf_event *event;
-
- list_for_each_entry_rcu(event, &ctx->event_list, event_entry) {
- if (perf_event_comm_match(event))
- perf_event_comm_output(event, comm_event);
- }
+ return event->attr.comm;
}
static void perf_event_comm_event(struct perf_comm_event *comm_event)
{
- struct perf_cpu_context *cpuctx;
- struct perf_event_context *ctx;
char comm[TASK_COMM_LEN];
unsigned int size;
- struct pmu *pmu;
- int ctxn;
memset(comm, 0, sizeof(comm));
strlcpy(comm, comm_event->task->comm, sizeof(comm));
@@ -4627,24 +4691,11 @@ static void perf_event_comm_event(struct perf_comm_event *comm_event)
comm_event->comm_size = size;
comm_event->event_id.header.size = sizeof(comm_event->event_id) + size;
- rcu_read_lock();
- list_for_each_entry_rcu(pmu, &pmus, entry) {
- cpuctx = get_cpu_ptr(pmu->pmu_cpu_context);
- if (cpuctx->unique_pmu != pmu)
- goto next;
- perf_event_comm_ctx(&cpuctx->ctx, comm_event);
- ctxn = pmu->task_ctx_nr;
- if (ctxn < 0)
- goto next;
-
- ctx = rcu_dereference(current->perf_event_ctxp[ctxn]);
- if (ctx)
- perf_event_comm_ctx(ctx, comm_event);
-next:
- put_cpu_ptr(pmu->pmu_cpu_context);
- }
- rcu_read_unlock();
+ perf_event_aux(perf_event_comm_match,
+ perf_event_comm_output,
+ comm_event,
+ NULL);
}
void perf_event_comm(struct task_struct *task)
@@ -4706,8 +4757,9 @@ struct perf_mmap_event {
};
static void perf_event_mmap_output(struct perf_event *event,
- struct perf_mmap_event *mmap_event)
+ void *data)
{
+ struct perf_mmap_event *mmap_event = data;
struct perf_output_handle handle;
struct perf_sample_data sample;
int size = mmap_event->event_id.header.size;
@@ -4734,46 +4786,24 @@ out:
}
static int perf_event_mmap_match(struct perf_event *event,
- struct perf_mmap_event *mmap_event,
- int executable)
+ void *data)
{
- if (event->state < PERF_EVENT_STATE_INACTIVE)
- return 0;
-
- if (!event_filter_match(event))
- return 0;
-
- if ((!executable && event->attr.mmap_data) ||
- (executable && event->attr.mmap))
- return 1;
-
- return 0;
-}
-
-static void perf_event_mmap_ctx(struct perf_event_context *ctx,
- struct perf_mmap_event *mmap_event,
- int executable)
-{
- struct perf_event *event;
+ struct perf_mmap_event *mmap_event = data;
+ struct vm_area_struct *vma = mmap_event->vma;
+ int executable = vma->vm_flags & VM_EXEC;
- list_for_each_entry_rcu(event, &ctx->event_list, event_entry) {
- if (perf_event_mmap_match(event, mmap_event, executable))
- perf_event_mmap_output(event, mmap_event);
- }
+ return (!executable && event->attr.mmap_data) ||
+ (executable && event->attr.mmap);
}
static void perf_event_mmap_event(struct perf_mmap_event *mmap_event)
{
- struct perf_cpu_context *cpuctx;
- struct perf_event_context *ctx;
struct vm_area_struct *vma = mmap_event->vma;
struct file *file = vma->vm_file;
unsigned int size;
char tmp[16];
char *buf = NULL;
const char *name;
- struct pmu *pmu;
- int ctxn;
memset(tmp, 0, sizeof(tmp));
@@ -4829,27 +4859,10 @@ got_name:
mmap_event->event_id.header.size = sizeof(mmap_event->event_id) + size;
- rcu_read_lock();
- list_for_each_entry_rcu(pmu, &pmus, entry) {
- cpuctx = get_cpu_ptr(pmu->pmu_cpu_context);
- if (cpuctx->unique_pmu != pmu)
- goto next;
- perf_event_mmap_ctx(&cpuctx->ctx, mmap_event,
- vma->vm_flags & VM_EXEC);
-
- ctxn = pmu->task_ctx_nr;
- if (ctxn < 0)
- goto next;
-
- ctx = rcu_dereference(current->perf_event_ctxp[ctxn]);
- if (ctx) {
- perf_event_mmap_ctx(ctx, mmap_event,
- vma->vm_flags & VM_EXEC);
- }
-next:
- put_cpu_ptr(pmu->pmu_cpu_context);
- }
- rcu_read_unlock();
+ perf_event_aux(perf_event_mmap_match,
+ perf_event_mmap_output,
+ mmap_event,
+ NULL);
kfree(buf);
}
@@ -6474,6 +6487,8 @@ set:
if (atomic_read(&event->mmap_count))
goto unlock;
+ old_rb = event->rb;
+
if (output_event) {
/* get the rb we want to redirect to */
rb = ring_buffer_get(output_event);
@@ -6481,16 +6496,28 @@ set:
goto unlock;
}
- old_rb = event->rb;
- rcu_assign_pointer(event->rb, rb);
if (old_rb)
ring_buffer_detach(event, old_rb);
+
+ if (rb)
+ ring_buffer_attach(event, rb);
+
+ rcu_assign_pointer(event->rb, rb);
+
+ if (old_rb) {
+ ring_buffer_put(old_rb);
+ /*
+ * Since we detached before setting the new rb, so that we
+ * could attach the new rb, we could have missed a wakeup.
+ * Provide it now.
+ */
+ wake_up_all(&event->waitq);
+ }
+
ret = 0;
unlock:
mutex_unlock(&event->mmap_mutex);
- if (old_rb)
- ring_buffer_put(old_rb);
out:
return ret;
}