[input] push and pop mutex cleanup around cancellation points #2837

NEWS.md

@@ -3,6 +3,10 @@ rearrangements of Notcurses.
 
 * 3.0.14 (not yet released)
   * `ncplane_family_destroy()` has been added to the API.
+  * Added some `foot` capabilities. Recognize `ghostty` and bless its
+     quadrants/sextants implementations.
+  * A bug introduced sometime in 2022 that caused unpredictable
+    hangs on exit was resolved (#2837), yay!
 
 * 3.0.13 (2025-01-11)
   * Fix regression when building with `USE_CXX=off`.

src/lib/in.c

@@ -2668,6 +2668,11 @@ int inputready_fd(const inputctx* ictx){
 #endif
 }
 
+static void
+cleanup_mutex(void* v){
+  pthread_mutex_unlock(v);
+}
+
 static inline uint32_t
 internal_get(inputctx* ictx, const struct timespec* ts, ncinput* ni){
   uint32_t id;
@@ -2690,10 +2695,16 @@ internal_get(inputctx* ictx, const struct timespec* ts, ncinput* ni){
       }
       return NCKEY_EOF;
     }
+    int r;
+    pthread_cleanup_push(cleanup_mutex, &ictx->ilock);
     if(ts == NULL){
-      pthread_cond_wait(&ictx->icond, &ictx->ilock);
+      r = pthread_cond_wait(&ictx->icond, &ictx->ilock);
     }else{
-      int r = pthread_cond_timedwait(&ictx->icond, &ictx->ilock, ts);
+      r = pthread_cond_timedwait(&ictx->icond, &ictx->ilock, ts);
+    }
+    pthread_cleanup_pop(0);
+    if(r){
+      pthread_mutex_unlock(&ictx->ilock);
       if(r == ETIMEDOUT){
         pthread_mutex_unlock(&ictx->ilock);
         if(ni){
@@ -2728,9 +2739,11 @@ internal_get(inputctx* ictx, const struct timespec* ts, ncinput* ni){
     logtrace("draining event readiness pipe %d", ictx->ivalid);
 #ifndef __MINGW32__
     char c;
+    pthread_cleanup_push(cleanup_mutex, &ictx->ilock);
     while(read(ictx->readypipes[0], &c, sizeof(c)) == 1){
       // FIXME accelerate?
     }
+    pthread_cleanup_pop(0);
 #else
     // we ought be draining this, but it breaks everything, as we can't easily
     // do nonblocking input from a pipe in windows, augh...