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Make android_select more robust

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* src/android.c (android_run_select_thread): Lock select_mutex
before signalling condition variable.
(android_select): Unlock event queue mutex prior to waiting for
it.
This commit is contained in:
Po Lu 2023-02-23 18:05:57 +08:00
parent 1d84465236
commit 8747568d69
1 changed files with 17 additions and 8 deletions
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25
src/android.c
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@ -387,12 +387,15 @@ android_run_select_thread (void *data)
android_pselect_rc = rc;
pthread_mutex_unlock (&event_queue.select_mutex);
/* Signal the main thread that there is now data to read.
It is ok to signal this condition variable without holding
the event queue lock, because android_select will always
wait for this to complete before returning. */
/* Signal the main thread that there is now data to read. Hold
the event queue lock during this process to make sure this
does not happen before the main thread begins to wait for the
condition variable. */
pthread_mutex_lock (&event_queue.select_mutex);
android_pselect_completed = true;
pthread_cond_broadcast (&event_queue.read_var);
pthread_mutex_unlock (&event_queue.select_mutex);
if (rc != -1 || errno != EINTR)
/* Now, wait for SIGUSR1, unless pselect was interrupted and
@ -635,13 +638,22 @@ android_select (int nfds, fd_set *readfds, fd_set *writefds,
"write: %s", strerror (errno));
#endif
/* Wait for pselect to return in any case. */
/* Unlock the event queue mutex. */
pthread_mutex_unlock (&event_queue.mutex);
/* Wait for pselect to return in any case. This must be done with
the event queue mutex unlocked. Otherwise, the pselect thread
can hang if it tries to lock the event queue mutex to signal
read_var after the UI thread has already done so. */
while (sem_wait (&android_pselect_sem) < 0)
;;
/* If there are now events in the queue, return 1. */
pthread_mutex_lock (&event_queue.mutex);
if (event_queue.num_events)
nfds_return = 1;
pthread_mutex_unlock (&event_queue.mutex);
/* Add the return value of pselect. */
if (android_pselect_rc >= 0)
@ -650,9 +662,6 @@ android_select (int nfds, fd_set *readfds, fd_set *writefds,
if (!nfds_return && android_pselect_rc < 0)
nfds_return = android_pselect_rc;
/* Unlock the event queue mutex. */
pthread_mutex_unlock (&event_queue.mutex);
/* This is to shut up process.c when pselect gets EINTR. */
if (nfds_return < 0)
errno = EINTR;