When QEMU is started with `-daemonize`, all stdio descriptors get
redirected to `/dev/null`. This basically means that anything
printed with `error_report()` and friends is lost.
One could hope that passing `-D ${logfile}` would cause the messages
to go to `${logfile}`, as the documentation tends to suggest:
-D logfile
Output log in logfile instead of to stderr
Unfortunately, `-D` belongs to the logging framework and it only
does this redirection if some log item is also enabled with `-d`
or if QEMU was configured with `--enable-trace-backend=log`. A
typical production setup doesn't do tracing or fine-grain
debugging but it certainly needs to collect errors.
Ignore the check on enabled log items when QEMU is daemonized. Previous
behaviour is retained for the non-daemonized case. The logic is unrolled
as a series of `if` for better readability.
Special care is needed for the `-D ${logfile} -d tid` case : `${logfile}`
is expected to be a template that contains exactly one `%d` that should be
expanded to a PID or TID. The logic in `qemu_log_trylock()` already takes
care of that for per-thread logs. Do it as well for the QEMU main thread
when opening the file.
Signed-off-by: Greg Kurz <gr...@kaod.org>
---
util/log.c | 39 ++++++++++++++++++++++++++++-----------
1 file changed, 28 insertions(+), 11 deletions(-)
diff --git a/util/log.c b/util/log.c
index d6eb0378c3a3..a4592fa9bb70 100644
--- a/util/log.c
+++ b/util/log.c
@@ -248,16 +248,21 @@ static bool qemu_set_log_internal(const char *filename,
bool changed_name,
#endif
qemu_loglevel = log_flags;
- /*
- * In all cases we only log if qemu_loglevel is set.
- * Also:
- * If per-thread, open the file for each thread in qemu_log_lock.
- * If not daemonized we will always log either to stderr
- * or to a file (if there is a filename).
- * If we are daemonized, we will only log if there is a filename.
- */
daemonized = is_daemonized();
- need_to_open_file = log_flags && !per_thread && (!daemonized || filename);
+ need_to_open_file = false;
+ if (!daemonized) {
+ /*
+ * If not daemonized we only log if qemu_loglevel is set, either to
+ * stderr or to a file (if there is a filename).
+ * If per-thread, open the file for each thread in qemu_log_trylock().
+ */
+ need_to_open_file = log_flags && !per_thread;
+ } else if (filename) {
+ /*
+ * If we are daemonized, we will only log if there is a filename.
+ */
+ need_to_open_file = true;
+ }
if (logfile && (!need_to_open_file || changed_name)) {
qatomic_rcu_set(&global_file, NULL);
@@ -271,10 +276,22 @@ static bool qemu_set_log_internal(const char *filename,
bool changed_name,
if (!logfile && need_to_open_file) {
if (filename) {
- logfile = fopen(filename, log_append ? "a" : "w");
+ g_autofree char *fname = NULL;
+
+ /*
+ * If per-thread, filename contains a single %d that should be
+ * converted.
+ */
+ if (per_thread) {
+ fname = g_strdup_printf(filename, getpid());
+ } else {
+ fname = g_strdup(filename);
+ }
+
+ logfile = fopen(fname, log_append ? "a" : "w");
if (!logfile) {
error_setg_errno(errp, errno, "Error opening logfile %s",
- filename);
+ fname);
return false;
}
/* In case we are a daemon redirect stderr to logfile */
--
2.37.3
