[PATCH 5.19 143/717] ring-buffer: Add ring_buffer_wake_waiters()

Greg Kroah-Hartman
2022-10-22T07:43:32Z

From: Steven Rostedt (Google) <rostedt@goodmis.org>

commit 7e9fbbb1b776d8d7969551565bc246f74ec53b27 upstream.

On closing of a file that represents a ring buffer or flushing the file,
there may be waiters on the ring buffer that needs to be woken up and exit
the ring_buffer_wait() function.

Add ring_buffer_wake_waiters() to wake up the waiters on the ring buffer
and allow them to exit the wait loop.

Link: https://lkml.kernel.org/r/20220928133938.28dc2c27@gandalf.local.home

Cc: stable@vger.kernel.org
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Fixes: 15693458c4bc0 ("tracing/ring-buffer: Move poll wake ups into ring buffer code")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/linux/ring_buffer.h | 2 +-
kernel/trace/ring_buffer.c | 39 +++++++++++++++++++++++++++++++++++++++
2 files changed, 40 insertions(+), 1 deletion(-)

--- a/include/linux/ring_buffer.h
+++ b/include/linux/ring_buffer.h
@@ -101,7 +101,7 @@ __ring_buffer_alloc(unsigned long size,
int ring_buffer_wait(struct trace_buffer *buffer, int cpu, int full);
__poll_t ring_buffer_poll_wait(struct trace_buffer *buffer, int cpu,
struct file *filp, poll_table *poll_table);
-
+void ring_buffer_wake_waiters(struct trace_buffer *buffer, int cpu);

#define RING_BUFFER_ALL_CPUS -1

--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -413,6 +413,7 @@ struct rb_irq_work {
struct irq_work work;
wait_queue_head_t waiters;
wait_queue_head_t full_waiters;
+ long wait_index;
bool waiters_pending;
bool full_waiters_pending;
bool wakeup_full;
@@ -925,6 +926,37 @@ static void rb_wake_up_waiters(struct ir
}

/**
+ * ring_buffer_wake_waiters - wake up any waiters on this ring buffer
+ * @buffer: The ring buffer to wake waiters on
+ *
+ * In the case of a file that represents a ring buffer is closing,
+ * it is prudent to wake up any waiters that are on this.
+ */
+void ring_buffer_wake_waiters(struct trace_buffer *buffer, int cpu)
+{
+ struct ring_buffer_per_cpu *cpu_buffer;
+ struct rb_irq_work *rbwork;
+
+ if (cpu == RING_BUFFER_ALL_CPUS) {
+
+ /* Wake up individual ones too. One level recursion */
+ for_each_buffer_cpu(buffer, cpu)
+ ring_buffer_wake_waiters(buffer, cpu);
+
+ rbwork = &buffer->irq_work;
+ } else {
+ cpu_buffer = buffer->buffers[cpu];
+ rbwork = &cpu_buffer->irq_work;
+ }
+
+ rbwork->wait_index++;
+ /* make sure the waiters see the new index */
+ smp_wmb();
+
+ rb_wake_up_waiters(&rbwork->work);
+}
+
+/**
* ring_buffer_wait - wait for input to the ring buffer
* @buffer: buffer to wait on
* @cpu: the cpu buffer to wait on
@@ -939,6 +971,7 @@ int ring_buffer_wait(struct trace_buffer
struct ring_buffer_per_cpu *cpu_buffer;
DEFINE_WAIT(wait);
struct rb_irq_work *work;
+ long wait_index;
int ret = 0;

/*
@@ -957,6 +990,7 @@ int ring_buffer_wait(struct trace_buffer
work = &cpu_buffer->irq_work;
}

+ wait_index = READ_ONCE(work->wait_index);

while (true) {
if (full)
@@ -1021,6 +1055,11 @@ int ring_buffer_wait(struct trace_buffer
}

schedule();
+
+ /* Make sure to see the new wait index */
+ smp_rmb();
+ if (wait_index != work->wait_index)
+ break;
}

if (full)