Commit e36f19a6 authored by Steven Rostedt (Google)'s avatar Steven Rostedt (Google)
Browse files

ring-buffer: Reuse rb_watermark_hit() for the poll logic 

The check for knowing if the poll should wait or not is basically the
exact same logic as rb_watermark_hit(). The only difference is that
rb_watermark_hit() also handles the !full case. But for the full case, the
logic is the same. Just call that instead of duplicating the code in
ring_buffer_poll_wait().

Link: https://lore.kernel.org/linux-trace-kernel/20240312131952.802267543@goodmis.org



Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: default avatarMasami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent 8145f1c3

kernel/trace/ring_buffer.c

+7 −14
Original line number Diff line number Diff line
@@ -960,25 +960,18 @@ __poll_t ring_buffer_poll_wait(struct trace_buffer *buffer, int cpu, 
	}



	if (full) {

		unsigned long flags;



		poll_wait(filp, &rbwork->full_waiters, poll_table);



		raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);

		if (!cpu_buffer->shortest_full ||

		    cpu_buffer->shortest_full > full)

			cpu_buffer->shortest_full = full;

		raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);

		if (full_hit(buffer, cpu, full))

		if (rb_watermark_hit(buffer, cpu, full))

			return EPOLLIN | EPOLLRDNORM;

		/*

		 * Only allow full_waiters_pending update to be seen after

		 * the shortest_full is set. If the writer sees the

		 * full_waiters_pending flag set, it will compare the

		 * amount in the ring buffer to shortest_full. If the amount

		 * in the ring buffer is greater than the shortest_full

		 * percent, it will call the irq_work handler to wake up

		 * this list. The irq_handler will reset shortest_full

		 * the shortest_full is set (in rb_watermark_hit). If the

		 * writer sees the full_waiters_pending flag set, it will

		 * compare the amount in the ring buffer to shortest_full.

		 * If the amount in the ring buffer is greater than the

		 * shortest_full percent, it will call the irq_work handler

		 * to wake up this list. The irq_handler will reset shortest_full

		 * back to zero. That's done under the reader_lock, but

		 * the below smp_mb() makes sure that the update to

		 * full_waiters_pending doesn't leak up into the above.