util/log: Close per-thread log file on thread termination

When `-D ${logfile} -d tid` is passed, qemu_log_trylock() creates
a dedicated log file for the current thread and opens it. The
corresponding file descriptor is cached in a __thread variable.
Nothing is done to close the corresponding file descriptor when the
thread terminates though and the file descriptor is leaked.

The issue was found during code inspection and reproduced manually.

Fix that with an atexit notifier.

Fixes: 4e51069d6793 ("util/log: Support per-thread log files")
Cc: richard.henderson@linaro.org
Signed-off-by: Greg Kurz <groug@kaod.org>
Message-Id: <20221021105734.555797-1-groug@kaod.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/util/log.c b/util/log.c
index d6eb0378c3a31572af62a4fa35e7ad5f83ce5093..39866bdaf2fa62bff555c15c5dd7fde1541c479a 100644 (file)
--- a/util/log.c
+++ b/util/log.c
@@ -42,6 +42,7 @@ static QemuMutex global_mutex;
 static char *global_filename;
 static FILE *global_file;
 static __thread FILE *thread_file;
+static __thread Notifier qemu_log_thread_cleanup_notifier;
 
 int qemu_loglevel;
 static bool log_append;
@@ -77,6 +78,12 @@ static int log_thread_id(void)
 #endif
 }
 
+static void qemu_log_thread_cleanup(Notifier *n, void *unused)
+{
+    fclose(thread_file);
+    thread_file = NULL;
+}
+
 /* Lock/unlock output. */
 
 FILE *qemu_log_trylock(void)
@@ -93,6 +100,8 @@ FILE *qemu_log_trylock(void)
                 return NULL;
             }
             thread_file = logfile;
+            qemu_log_thread_cleanup_notifier.notify = qemu_log_thread_cleanup;
+            qemu_thread_atexit_add(&qemu_log_thread_cleanup_notifier);
         } else {
             rcu_read_lock();
             /*