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Re: [PATCH 1/4] Add a mutex to guarantee single writer to qemu_logfile h
From: |
Alex Bennée |
Subject: |
Re: [PATCH 1/4] Add a mutex to guarantee single writer to qemu_logfile handle. |
Date: |
Thu, 07 Nov 2019 16:53:41 +0000 |
User-agent: |
mu4e 1.3.5; emacs 27.0.50 |
Robert Foley <address@hidden> writes:
> This is being added in preparation for using RCU with the logfile handle.
> Also added qemu_logfile_init() for initializing the logfile mutex.
>
> Signed-off-by: Robert Foley <address@hidden>
> ---
> util/log.c | 23 +++++++++++++++++++++++
> 1 file changed, 23 insertions(+)
>
> diff --git a/util/log.c b/util/log.c
> index 1ca13059ee..dff2f98c8c 100644
> --- a/util/log.c
> +++ b/util/log.c
> @@ -24,8 +24,11 @@
> #include "qapi/error.h"
> #include "qemu/cutils.h"
> #include "trace/control.h"
> +#include "qemu/thread.h"
>
> static char *logfilename;
> +static bool qemu_logfile_initialized;
> +static QemuMutex qemu_logfile_mutex;
> FILE *qemu_logfile;
> int qemu_loglevel;
> static int log_append = 0;
> @@ -49,6 +52,14 @@ int qemu_log(const char *fmt, ...)
> return ret;
> }
>
> +static void qemu_logfile_init(void)
> +{
> + if (!qemu_logfile_initialized) {
> + qemu_mutex_init(&qemu_logfile_mutex);
> + qemu_logfile_initialized = true;
> + }
> +}
> +
> static bool log_uses_own_buffers;
>
> /* enable or disable low levels log */
> @@ -58,6 +69,12 @@ void qemu_set_log(int log_flags)
> #ifdef CONFIG_TRACE_LOG
> qemu_loglevel |= LOG_TRACE;
> #endif
> +
> + /* Is there a better place to call this to init the logfile subsystem? */
> + if (!qemu_logfile_initialized) {
> + qemu_logfile_init();
> + }
It wouldn't be the worst thing in the world to expose:
qemu_logfile_init()
and make vl.c and main.c call it before the setup. Then you can drop the
flag or even just g_assert(qemu_log_mutex_initialised) in qemu_set_log
and qemu_set_logfile.
In fact you could just use:
static void __attribute__((__constructor__)) qemu_logfile_init(void)
and make the compiler do it for you.
> + qemu_mutex_lock(&qemu_logfile_mutex);
> if (!qemu_logfile &&
> (is_daemonized() ? logfilename != NULL : qemu_loglevel)) {
> if (logfilename) {
> @@ -93,6 +110,7 @@ void qemu_set_log(int log_flags)
> log_append = 1;
> }
> }
> + qemu_mutex_unlock(&qemu_logfile_mutex);
> if (qemu_logfile &&
> (is_daemonized() ? logfilename == NULL : !qemu_loglevel)) {
> qemu_log_close();
> @@ -114,6 +132,11 @@ void qemu_set_log_filename(const char *filename, Error
> **errp)
> char *pidstr;
> g_free(logfilename);
>
> + /* Is there a better place to call this to init the logfile subsystem? */
> + if (!qemu_logfile_initialized) {
> + qemu_logfile_init();
> + }
> +
> pidstr = strstr(filename, "%");
> if (pidstr) {
> /* We only accept one %d, no other format strings */
--
Alex Bennée