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Re: [Qemu-devel] [PATCH v5] log: Make glib logging go through QEMU


From: Markus Armbruster
Subject: Re: [Qemu-devel] [PATCH v5] log: Make glib logging go through QEMU
Date: Thu, 24 Jan 2019 17:10:28 +0100
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux)

Christophe Fergeau <address@hidden> writes:

> This commit adds a qemu_init_logging() helper which calls
> g_log_set_default_handler() so that glib logs (g_log, g_warning, ...)
> are handled similarly to other QEMU logs. This means they will get a
> timestamp if timestamps are enabled, and they will go through the
> monitor if one is configured.

s/monitor/HMP monitor/

I see why one would like to extend the timestamp feature to GLib log
messages.  Routing them through the HMP monitor is perhaps debatable.
Cc: Dave in case he has an opinion.

> This commit also adds a call to qemu_init_logging() to the binaries
> installed by QEMU.
> glib debug messages are enabled through G_MESSAGES_DEBUG similarly to
> glib default log handler.
>
> At the moment, this change will mostly impact SPICE logging if your
> spice version is >= 0.14.1. With older spice versions, this is not going
> to work as expected, but will not have any ill effect, so this call is
> not conditional on the SPICE version.
>
> Signed-off-by: Christophe Fergeau <address@hidden>
> Reviewed-by: Daniel P. Berrangé <address@hidden>
> Reviewed-by: Stefan Hajnoczi <address@hidden>
> ---
> One more iteration of the patch as it hit CI failures
> (https://patchew.org/QEMU/address@hidden/ )
> Only difference from v4 is the addition of #include "qemu/error-report.h"
> in bsd-user and linux-user.
>
>
>  bsd-user/main.c             |  2 ++
>  include/qemu/error-report.h |  2 ++
>  linux-user/main.c           |  2 ++
>  qemu-img.c                  |  1 +
>  qemu-io.c                   |  1 +
>  qemu-nbd.c                  |  1 +
>  scsi/qemu-pr-helper.c       |  1 +
>  util/qemu-error.c           | 47 +++++++++++++++++++++++++++++++++++++
>  vl.c                        |  1 +
>  9 files changed, 58 insertions(+)
>
> diff --git a/bsd-user/main.c b/bsd-user/main.c
> index 0d3156974c..0df5c853d3 100644
> --- a/bsd-user/main.c
> +++ b/bsd-user/main.c
> @@ -24,6 +24,7 @@
>  #include "qapi/error.h"
>  #include "qemu.h"
>  #include "qemu/config-file.h"
> +#include "qemu/error-report.h"
>  #include "qemu/path.h"
>  #include "qemu/help_option.h"
>  #include "cpu.h"
> @@ -743,6 +744,7 @@ int main(int argc, char **argv)
>      if (argc <= 1)
>          usage();
>  
> +    qemu_init_logging();
>      module_call_init(MODULE_INIT_TRACE);
>      qemu_init_cpu_list();
>      module_call_init(MODULE_INIT_QOM);
> diff --git a/include/qemu/error-report.h b/include/qemu/error-report.h
> index 0a8d9cc9ea..2852e9df2a 100644
> --- a/include/qemu/error-report.h
> +++ b/include/qemu/error-report.h
> @@ -49,6 +49,8 @@ bool error_report_once_cond(bool *printed, const char *fmt, 
> ...)
>  bool warn_report_once_cond(bool *printed, const char *fmt, ...)
>      GCC_FMT_ATTR(2, 3);
>  
> +void qemu_init_logging(void);
> +
>  /*
>   * Similar to error_report(), except it prints the message just once.
>   * Return true when it prints, false otherwise.
> diff --git a/linux-user/main.c b/linux-user/main.c
> index a0aba9cb1e..d9b3ffd1f4 100644
> --- a/linux-user/main.c
> +++ b/linux-user/main.c
> @@ -27,6 +27,7 @@
>  #include "qemu/path.h"
>  #include "qemu/config-file.h"
>  #include "qemu/cutils.h"
> +#include "qemu/error-report.h"
>  #include "qemu/help_option.h"
>  #include "cpu.h"
>  #include "exec/exec-all.h"
> @@ -600,6 +601,7 @@ int main(int argc, char **argv, char **envp)
>      int ret;
>      int execfd;
>  
> +    qemu_init_logging();
>      module_call_init(MODULE_INIT_TRACE);
>      qemu_init_cpu_list();
>      module_call_init(MODULE_INIT_QOM);
> diff --git a/qemu-img.c b/qemu-img.c
> index ad04f59565..9214392565 100644
> --- a/qemu-img.c
> +++ b/qemu-img.c
> @@ -4912,6 +4912,7 @@ int main(int argc, char **argv)
>      signal(SIGPIPE, SIG_IGN);
>  #endif
>  
> +    qemu_init_logging();
>      module_call_init(MODULE_INIT_TRACE);
>      error_set_progname(argv[0]);
>      qemu_init_exec_dir(argv[0]);
> diff --git a/qemu-io.c b/qemu-io.c
> index 6df7731af4..ad38d12e68 100644
> --- a/qemu-io.c
> +++ b/qemu-io.c
> @@ -524,6 +524,7 @@ int main(int argc, char **argv)
>      signal(SIGPIPE, SIG_IGN);
>  #endif
>  
> +    qemu_init_logging();
>      module_call_init(MODULE_INIT_TRACE);
>      progname = g_path_get_basename(argv[0]);
>      qemu_init_exec_dir(argv[0]);
> diff --git a/qemu-nbd.c b/qemu-nbd.c
> index 51b55f2e06..274b22d445 100644
> --- a/qemu-nbd.c
> +++ b/qemu-nbd.c
> @@ -581,6 +581,7 @@ int main(int argc, char **argv)
>      signal(SIGPIPE, SIG_IGN);
>  #endif
>  
> +    qemu_init_logging();
>      module_call_init(MODULE_INIT_TRACE);
>      error_set_progname(argv[0]);
>      qcrypto_init(&error_fatal);
> diff --git a/scsi/qemu-pr-helper.c b/scsi/qemu-pr-helper.c
> index e7af637232..523f8b237c 100644
> --- a/scsi/qemu-pr-helper.c
> +++ b/scsi/qemu-pr-helper.c
> @@ -895,6 +895,7 @@ int main(int argc, char **argv)
>  
>      signal(SIGPIPE, SIG_IGN);
>  
> +    qemu_init_logging();
>      module_call_init(MODULE_INIT_TRACE);
>      module_call_init(MODULE_INIT_QOM);
>      qemu_add_opts(&qemu_trace_opts);
> diff --git a/util/qemu-error.c b/util/qemu-error.c
> index fcbe8a1f74..1118ed4695 100644
> --- a/util/qemu-error.c
> +++ b/util/qemu-error.c
> @@ -345,3 +345,50 @@ bool warn_report_once_cond(bool *printed, const char 
> *fmt, ...)
>      va_end(ap);
>      return true;
>  }
> +
> +static char *qemu_glog_domains;
> +
> +static void qemu_log_func(const gchar *log_domain,
> +                          GLogLevelFlags log_level,
> +                          const gchar *message,
> +                          gpointer user_data)
> +{
> +    switch (log_level & G_LOG_LEVEL_MASK) {
> +    case G_LOG_LEVEL_DEBUG:
> +        /* Use same G_MESSAGES_DEBUG logic as glib to enable/disable debug
> +         * messages
> +         */

Wing both ends of the comment, please.

> +        if (qemu_glog_domains == NULL) {
> +            break;
> +        }
> +        if (strcmp(qemu_glog_domains, "all") != 0 &&
> +          (log_domain == NULL || !strstr(qemu_glog_domains, log_domain))) {
> +            break;
> +        }
> +        /* Fall through */
> +    case G_LOG_LEVEL_INFO:
> +        /* Fall through */

g_log_default_handler() applies G_MESSAGES_DEBUG suppression logic to
G_LOG_LEVEL_INFO messages, too.  Do you deviate intentionally?

> +    case G_LOG_LEVEL_MESSAGE:
> +        info_report("%s: %s", log_domain, message);

@log_domain can be null.  You even check for that above.

> +        break;
> +    case G_LOG_LEVEL_WARNING:
> +        warn_report("%s: %s", log_domain, message);
> +        break;
> +    case G_LOG_LEVEL_CRITICAL:
> +        /* Fall through */
> +    case G_LOG_LEVEL_ERROR:
> +        error_report("%s: %s", log_domain, message);
> +        break;

Sure we don't need to check for G_LOG_FLAG_RECURSION?
g_log_default_handler() has a conditional for that...

Not sure it has anything for G_LOG_FLAG_FATAL; it's code is surprisingly
complex.

> +    }
> +}
> +
> +/*
> + * Init QEMU logging subsystem. This sets up glib logging so libraries using 
> it
> + * also print their logs through {info,warn,error}_report.
> + */

Format like the other function comments:

   /*
    * Init QEMU logging subsystem.
    * This sets up glib logging so libraries using it also print their logs
    * through error_report(), warn_report(), info_report().
    */

Braces expanded for better grepability.

> +void qemu_init_logging(void)

Naming is hard...  Yes, this "initializes logging" in a sense: it
installs a GLib default log handler that routes GLib log messages
through this module.  But that's detail; the callers don't care what
this function does, all they care for is "must call early".  If this
module ever grows a need to initialize something else before it gets
used, we'll regret naming its initialization function
qemu_init_logging().

Hmm, it has already grown such a need: initializing @progname.
error_set_progname() does it.  Asking a module's users to call *two*
initializtion functions is not nice.

Fuse the two into error_init(const char *argv0)?

> +{
> +    g_log_set_default_handler(qemu_log_func, NULL);
> +    g_warn_if_fail(qemu_glog_domains == NULL);
> +    qemu_glog_domains = g_strdup(g_getenv("G_MESSAGES_DEBUG"));
> +}
> diff --git a/vl.c b/vl.c
> index bc9fbec654..f03f20e060 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -3039,6 +3039,7 @@ int main(int argc, char **argv, char **envp)
>      QSIMPLEQ_HEAD(, BlockdevOptions_queue) bdo_queue
>          = QSIMPLEQ_HEAD_INITIALIZER(bdo_queue);
>  
> +    qemu_init_logging();
>      module_call_init(MODULE_INIT_TRACE);
>  
>      qemu_init_cpu_list();



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