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togglerecord: define total order on mutexes

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I'm tracking a bug which may or may not be related to a deadlock in
togglerecord.

I audited the code and figured we could define a total order on the
mutexes with just a few changes.
I don't know yet if that will help with my bug but it can't hurt to have
a order properly documented with so many mutexes involved.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/merge_requests/1935>
This commit is contained in:
Guillaume Desmottes 2024-11-21 14:34:37 +01:00 committed by GStreamer Marge Bot
parent 20fb4f82d8
commit 5f007ed7ee
1 changed files with 12 additions and 4 deletions
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16
utils/togglerecord/src/togglerecord/imp.rs
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@ -26,6 +26,12 @@ use std::sync::LazyLock;
const DEFAULT_RECORD: bool = false; const DEFAULT_RECORD: bool = false;
const DEFAULT_LIVE: bool = false; const DEFAULT_LIVE: bool = false;
// Mutex order:
// - self.state (used with self.main_stream_cond)
// - self.main_stream.state
// - stream.state with stream coming from either self.state.pads or self.state.other_streams
// - self.settings
#[derive(Debug, Clone, Copy)] #[derive(Debug, Clone, Copy)]
struct Settings { struct Settings {
record: bool, record: bool,
@ -367,7 +373,7 @@ impl ToggleRecord {
&self, &self,
pad: &gst::Pad, pad: &gst::Pad,
mut settings: Settings, mut settings: Settings,
stream: &Stream, stream: &Stream, // main stream
upstream_live: bool, upstream_live: bool,
) -> Result<bool, gst::FlowError> { ) -> Result<bool, gst::FlowError> {
if !upstream_live { if !upstream_live {
@ -394,6 +400,7 @@ impl ToggleRecord {
state.segment_pending = true; state.segment_pending = true;
state.discont_pending = true; state.discont_pending = true;
for other_stream in &rec_state.other_streams.0 { for other_stream in &rec_state.other_streams.0 {
// safe from deadlock as `state` is a lock on the main stream which is not in `other_streams`
let mut other_state = other_stream.state.lock(); let mut other_state = other_stream.state.lock();
other_state.segment_pending = true; other_state.segment_pending = true;
other_state.discont_pending = true; other_state.discont_pending = true;
@ -556,6 +563,7 @@ impl ToggleRecord {
while !state.flushing while !state.flushing
&& !rec_state.other_streams.0.iter().all(|s| { && !rec_state.other_streams.0.iter().all(|s| {
// safe from deadlock as `state` is a lock on the main stream which is not in `other_streams`
let s = s.state.lock(); let s = s.state.lock();
s.eos s.eos
|| s.current_running_time || s.current_running_time
@ -662,6 +670,7 @@ impl ToggleRecord {
state.segment_pending = true; state.segment_pending = true;
state.discont_pending = true; state.discont_pending = true;
for other_stream in &rec_state.other_streams.0 { for other_stream in &rec_state.other_streams.0 {
// safe from deadlock as `state` is a lock on the main stream which is not in `other_streams`
let mut other_state = other_stream.state.lock(); let mut other_state = other_stream.state.lock();
other_state.segment_pending = true; other_state.segment_pending = true;
other_state.discont_pending = true; other_state.discont_pending = true;
@ -785,13 +794,12 @@ impl ToggleRecord {
drop(state); drop(state);
let mut rec_state = self.state.lock();
let mut main_state = self.main_stream.state.lock();
// Wake up, in case the main stream is waiting for us to progress up to here. We progressed // Wake up, in case the main stream is waiting for us to progress up to here. We progressed
// above but all notifying must happen while the main_stream state is locked as per above. // above but all notifying must happen while the main_stream state is locked as per above.
self.main_stream_cond.notify_all(); self.main_stream_cond.notify_all();
let mut rec_state = self.state.lock();
let mut main_state = self.main_stream.state.lock();
state = stream.state.lock(); state = stream.state.lock();
// Wait until the main stream advanced completely past our current running time in // Wait until the main stream advanced completely past our current running time in