[v1,1/5] Add a mutex to guarantee single writer to qemu_logfile handle.

Also added qemu_logfile_init() for initializing the logfile mutex.

Signed-off-by: Robert Foley <robert.foley@linaro.org>
---
v1
    - changed qemu_logfile_init() to use __constructor__.
---
 util/log.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

Robert Foley <robert.foley@linaro.org> writes:

> Also added qemu_logfile_init() for initializing the logfile mutex.
>
> Signed-off-by: Robert Foley <robert.foley@linaro.org>

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

> ---
> v1
>     - changed qemu_logfile_init() to use __constructor__.
> ---
>  util/log.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
>
> diff --git a/util/log.c b/util/log.c
> index 1ca13059ee..c25643dc99 100644
> --- a/util/log.c
> +++ b/util/log.c
> @@ -24,8 +24,10 @@
>  #include "qapi/error.h"
>  #include "qemu/cutils.h"
>  #include "trace/control.h"
> +#include "qemu/thread.h"
>
>  static char *logfilename;
> +static QemuMutex qemu_logfile_mutex;
>  FILE *qemu_logfile;
>  int qemu_loglevel;
>  static int log_append = 0;
> @@ -49,6 +51,11 @@ int qemu_log(const char *fmt, ...)
>      return ret;
>  }
>
> +static void __attribute__((__constructor__)) qemu_logfile_init(void)
> +{
> +    qemu_mutex_init(&qemu_logfile_mutex);
> +}
> +
>  static bool log_uses_own_buffers;
>
>  /* enable or disable low levels log */
> @@ -58,6 +65,9 @@ void qemu_set_log(int log_flags)
>  #ifdef CONFIG_TRACE_LOG
>      qemu_loglevel |= LOG_TRACE;
>  #endif
> +
> +    g_assert(qemu_logfile_mutex.initialized);
> +    qemu_mutex_lock(&qemu_logfile_mutex);
>      if (!qemu_logfile &&
>          (is_daemonized() ? logfilename != NULL : qemu_loglevel)) {
>          if (logfilename) {
> @@ -93,6 +103,7 @@ 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();
> @@ -230,12 +241,15 @@ void qemu_log_flush(void)
>  /* Close the log file */
>  void qemu_log_close(void)
>  {
> +    g_assert(qemu_logfile_mutex.initialized);
> +    qemu_mutex_lock(&qemu_logfile_mutex);
>      if (qemu_logfile) {
>          if (qemu_logfile != stderr) {
>              fclose(qemu_logfile);
>          }
>          qemu_logfile = NULL;
>      }
> +    qemu_mutex_unlock(&qemu_logfile_mutex);
>  }
>
>  const QEMULogItem qemu_log_items[] = {


--
Alex Bennée

On 11/12/19 4:01 PM, Robert Foley wrote:
> Also added qemu_logfile_init() for initializing the logfile mutex.
> 
> Signed-off-by: Robert Foley <robert.foley@linaro.org>
> ---
> v1
>     - changed qemu_logfile_init() to use __constructor__.
> ---
>  util/log.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/util/log.c b/util/log.c
> index 1ca13059ee..c25643dc99 100644
> --- a/util/log.c
> +++ b/util/log.c
> @@ -24,8 +24,10 @@
>  #include "qapi/error.h"
>  #include "qemu/cutils.h"
>  #include "trace/control.h"
> +#include "qemu/thread.h"
>  
>  static char *logfilename;
> +static QemuMutex qemu_logfile_mutex;
>  FILE *qemu_logfile;
>  int qemu_loglevel;
>  static int log_append = 0;
> @@ -49,6 +51,11 @@ int qemu_log(const char *fmt, ...)
>      return ret;
>  }
>  
> +static void __attribute__((__constructor__)) qemu_logfile_init(void)
> +{
> +    qemu_mutex_init(&qemu_logfile_mutex);
> +}
> +
>  static bool log_uses_own_buffers;
>  
>  /* enable or disable low levels log */
> @@ -58,6 +65,9 @@ void qemu_set_log(int log_flags)
>  #ifdef CONFIG_TRACE_LOG
>      qemu_loglevel |= LOG_TRACE;
>  #endif
> +
> +    g_assert(qemu_logfile_mutex.initialized);

Why the asserts?

If you want a runtime test, then use the test to initialize it.
Otherwise, trust the constructor.


r~

> > +
> > +    g_assert(qemu_logfile_mutex.initialized);
>
> Why the asserts?
>
> If you want a runtime test, then use the test to initialize it.
> Otherwise, trust the constructor.
>
I see your point here.   We can/should just trust the constructor.
Will remove the mutex.initialized asserts.

Thanks,
-Rob

On Sat, 16 Nov 2019 at 06:58, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> On 11/12/19 4:01 PM, Robert Foley wrote:
> > Also added qemu_logfile_init() for initializing the logfile mutex.
> >
> > Signed-off-by: Robert Foley <robert.foley@linaro.org>
> > ---
> > v1
> >     - changed qemu_logfile_init() to use __constructor__.
> > ---
> >  util/log.c | 14 ++++++++++++++
> >  1 file changed, 14 insertions(+)
> >
> > diff --git a/util/log.c b/util/log.c
> > index 1ca13059ee..c25643dc99 100644
> > --- a/util/log.c
> > +++ b/util/log.c
> > @@ -24,8 +24,10 @@
> >  #include "qapi/error.h"
> >  #include "qemu/cutils.h"
> >  #include "trace/control.h"
> > +#include "qemu/thread.h"
> >
> >  static char *logfilename;
> > +static QemuMutex qemu_logfile_mutex;
> >  FILE *qemu_logfile;
> >  int qemu_loglevel;
> >  static int log_append = 0;
> > @@ -49,6 +51,11 @@ int qemu_log(const char *fmt, ...)
> >      return ret;
> >  }
> >
> > +static void __attribute__((__constructor__)) qemu_logfile_init(void)
> > +{
> > +    qemu_mutex_init(&qemu_logfile_mutex);
> > +}
> > +
> >  static bool log_uses_own_buffers;
> >
> >  /* enable or disable low levels log */
> > @@ -58,6 +65,9 @@ void qemu_set_log(int log_flags)
> >  #ifdef CONFIG_TRACE_LOG
> >      qemu_loglevel |= LOG_TRACE;
> >  #endif
> > +
> > +    g_assert(qemu_logfile_mutex.initialized);
>
> Why the asserts?
>
> If you want a runtime test, then use the test to initialize it.
> Otherwise, trust the constructor.
>
>
> r~