This is a note to let you know that I've just added the patch titled
tracing: Add ioctl() to force ring buffer waiters to wake up
to the 5.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tracing-add-ioctl-to-force-ring-buffer-waiters-to-wake-up.patch
and it can be found in the queue-5.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 01b2a52171735c6eea80ee2f355f32bea6c41418 Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (Google)" <rostedt@xxxxxxxxxxx>
Date: Thu, 29 Sep 2022 09:50:29 -0400
Subject: tracing: Add ioctl() to force ring buffer waiters to wake up
From: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
commit 01b2a52171735c6eea80ee2f355f32bea6c41418 upstream.
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@xxxxxxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Fixes: e30f53aad2202 ("tracing: Do not busy wait in buffer splice")
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/trace/trace.c | 22 ++++++++++++++++++++++
1 file changed, 22 insertions(+)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -8353,12 +8353,34 @@ 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,
};
Patches currently in stable-queue which might be from rostedt@xxxxxxxxxxx are
queue-5.19/tracing-fix-reading-strings-from-synthetic-events.patch
queue-5.19/tracing-add-ioctl-to-force-ring-buffer-waiters-to-wake-up.patch
queue-5.19/ring-buffer-have-the-shortest_full-queue-be-the-shortest-not-longest.patch
queue-5.19/ring-buffer-add-ring_buffer_wake_waiters.patch
queue-5.19/tracing-move-duplicate-code-of-trace_kprobe-eprobe.c-into-header.patch
queue-5.19/tracing-add-fault-name-injection-to-kernel-probes.patch
queue-5.19/ring-buffer-fix-race-between-reset-page-and-reading-page.patch
queue-5.19/tracing-wake-up-ring-buffer-waiters-on-closing-of-the-file.patch
queue-5.19/ftrace-still-disable-enabled-records-marked-as-disabled.patch
queue-5.19/tracing-disable-interrupt-or-preemption-before-acquiring-arch_spinlock_t.patch
queue-5.19/tracing-do-not-free-snapshot-if-tracer-is-on-cmdline.patch
queue-5.19/tracing-wake-up-waiters-when-tracing-is-disabled.patch
queue-5.19/ring-buffer-allow-splice-to-read-previous-partially-read-pages.patch
queue-5.19/ring-buffer-check-pending-waiters-when-doing-wake-ups-as-well.patch
queue-5.19/ftrace-properly-unset-ftrace_hash_fl_mod.patch
