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authorSteven Rostedt (Google) <rostedt@goodmis.org>2022-09-29 16:50:29 +0300
committerSteven Rostedt (Google) <rostedt@goodmis.org>2022-09-29 17:17:18 +0300
commit01b2a52171735c6eea80ee2f355f32bea6c41418 (patch)
treedaa9d3bb9f277cad521a324f7be355b077740122 /kernel/trace
parentf3ddb74ad0790030c9592229fb14d8c451f4e9a8 (diff)
downloadlinux-01b2a52171735c6eea80ee2f355f32bea6c41418.tar.xz
tracing: Add ioctl() to force ring buffer waiters to wake up
If a process is waiting on the ring buffer for data, there currently isn't a clean way to force it to wake up. Add an ioctl call that will force any tasks that are waiting on the trace_pipe_raw file to wake up. Link: https://lkml.kernel.org/r/20220929095029.117f913f@gandalf.local.home Cc: stable@vger.kernel.org Cc: Ingo Molnar <mingo@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Fixes: e30f53aad2202 ("tracing: Do not busy wait in buffer splice") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace')
-rw-r--r--kernel/trace/trace.c22
1 files changed, 22 insertions, 0 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index e101b0764b39..58afc83afc9d 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -8349,12 +8349,34 @@ out:
return ret;
}
+/* An ioctl call with cmd 0 to the ring buffer file will wake up all waiters */
+static long tracing_buffers_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+ struct ftrace_buffer_info *info = file->private_data;
+ struct trace_iterator *iter = &info->iter;
+
+ if (cmd)
+ return -ENOIOCTLCMD;
+
+ mutex_lock(&trace_types_lock);
+
+ iter->wait_index++;
+ /* Make sure the waiters see the new wait_index */
+ smp_wmb();
+
+ ring_buffer_wake_waiters(iter->array_buffer->buffer, iter->cpu_file);
+
+ mutex_unlock(&trace_types_lock);
+ return 0;
+}
+
static const struct file_operations tracing_buffers_fops = {
.open = tracing_buffers_open,
.read = tracing_buffers_read,
.poll = tracing_buffers_poll,
.release = tracing_buffers_release,
.splice_read = tracing_buffers_splice_read,
+ .unlocked_ioctl = tracing_buffers_ioctl,
.llseek = no_llseek,
};