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Revert "loop: don't call the hooks around blocking wait"

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This reverts commit 46dfa69f26.

We do actually need to release the locks for now. The reason is that
pipewire core will at various points do a blocking invoke into the
thread-loop (which is the data-loop when using non-rt/async processing)
to synchronize state. Because these functions are called with the
thread-loop lock and from some other thread (like gstreamer) it causes
a deadlock because the thread-loop is locked and can't run and the
caller is waiting for the thread-loop to complete.

See #4472
This commit is contained in:
Wim Taymans 2025-06-26 12:39:06 +02:00
parent ff60e68a23
commit 060d0e1761
2 changed files with 9 additions and 5 deletions
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10
spa/include/spa/support/loop.h
View file

@ -119,11 +119,11 @@ struct spa_loop_methods {
* an object that has identity. * an object that has identity.
* \param size The size of data to copy. * \param size The size of data to copy.
* \param block If \true, do not return until func has been called. Otherwise, * \param block If \true, do not return until func has been called. Otherwise,
* returns immediately. Passing \true can cause a deadlock when * returns immediately. Passing \true does not risk a deadlock because
* the calling thread is holding the loop context lock. A blocking * the data thread is never allowed to wait on any other thread.
* invoke should never be done from a realtime thread. Also beware * It the loop requires some locking, it must be acquired before
* of blocking invokes between 2 threads as you can easily end up * calling this function because a blocking invoke will release
* in a deadly embrace. * the lock while blocking.
* \param user_data An opaque pointer passed to func. * \param user_data An opaque pointer passed to func.
* \return `-EPIPE` if the internal ring buffer filled up, * \return `-EPIPE` if the internal ring buffer filled up,
* if block is \false, 0 if seq was SPA_ID_INVALID or * if block is \false, 0 if seq was SPA_ID_INVALID or

4
spa/plugins/support/loop.c
View file

@ -472,10 +472,14 @@ again:
if (block && queue->ack_fd != -1) { if (block && queue->ack_fd != -1) {
uint64_t count = 1; uint64_t count = 1;
spa_loop_control_hook_before(&impl->hooks_list);
if ((res = spa_system_eventfd_read(impl->system, queue->ack_fd, &count)) < 0) if ((res = spa_system_eventfd_read(impl->system, queue->ack_fd, &count)) < 0)
spa_log_warn(impl->log, "%p: failed to read event fd:%d: %s", spa_log_warn(impl->log, "%p: failed to read event fd:%d: %s",
queue, queue->ack_fd, spa_strerror(res)); queue, queue->ack_fd, spa_strerror(res));
spa_loop_control_hook_after(&impl->hooks_list);
res = item->res; res = item->res;
} }
else { else {