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: 15693458c4bc0 ("tracing/ring-buffer: Move poll wake ups into ring buffer code")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h
index dac53fd3afea33575f2addbab4db1382b5a737d3..2504df9a0453e6cfdcec454db7d56728b329cb23 100644 (file)
--- a/include/linux/ring_buffer.h
+++ b/include/linux/ring_buffer.h
@@ -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
 

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 5a7d818ca3ea381dfc4e413b2b5b21483b11a9f0..3046deacf7b332a8d978a7bff0b7a1abdfd146c0 100644 (file)
--- 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;
@@ -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)