Commit 7e9fbbb1 authored by Steven Rostedt (Google)'s avatar Steven Rostedt (Google)
Browse files

ring-buffer: Add ring_buffer_wake_waiters() 

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: 15693458 ("tracing/ring-buffer: Move poll wake ups into ring buffer code")
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent ec0bbc5e

include/linux/ring_buffer.h

+1 −1
Original line number Diff line number Diff line
@@ -101,7 +101,7 @@ __ring_buffer_alloc(unsigned long size, unsigned flags, struct lock_class_key *k 
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

kernel/trace/ring_buffer.c

+39 −0
Original line number Diff line number Diff line
@@ -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;
@@ -924,6 +925,37 @@ static void rb_wake_up_waiters(struct irq_work *work) 
	}

}



/**

 * 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
@@ -939,6 +971,7 @@ int ring_buffer_wait(struct trace_buffer *buffer, int cpu, int full) 
	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 *buffer, int cpu, int full) 
		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 *buffer, int cpu, int full) 
		}



		schedule();



		/* Make sure to see the new wait index */

		smp_rmb();

		if (wait_index != work->wait_index)

			break;

	}



	if (full)