util/log: Rename qemu_log_lock to qemu_log_trylock

This function can fail, which makes it more like ftrylockfile
or pthread_mutex_trylock than flockfile or pthread_mutex_lock,
so rename it.

To closer match the other trylock functions, release rcu_read_lock
along the failure path, so that qemu_log_unlock need not be called
on failure.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220417183019.755276-8-richard.henderson@linaro.org>

include/exec/log.h

@@ -71,7 +71,7 @@ static inline void log_disas(const void *code, unsigned long size)
 /* page_dump() output to the log file: */
 static inline void log_page_dump(const char *operation)
 {
-    FILE *logfile = qemu_log_lock();
+    FILE *logfile = qemu_log_trylock();
     if (logfile) {
         qemu_log("page layout changed following %s\n", operation);
         page_dump(logfile);