[Qemu-devel] [PATCH 0/3] qemu-error: advanced report_once handling

[Qemu-devel] [PATCH 0/3] qemu-error: advanced report_once handling

[Cornelia Huck]

Based on previous discussions, I wanted to enhance the recently
merged report_once infrastucture with a way to print a message
once based on a variable instead of globally-once, similar to
what vfio-ccw uses today.

Not really tested, mainly wanted to get this out before my vacation
to get the ball rolling.

Cornelia Huck (3):
  qemu-error: add {error,warn}_report_once_cond
  qemu-error: make use of {error,warn}_report_once_cond
  vfio-ccw: switch to warn_report_once_cond()

 hw/vfio/ccw.c               | 18 +++---------------
 include/qemu/error-report.h | 15 +++++++--------
 util/qemu-error.c           | 44 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 54 insertions(+), 23 deletions(-)

-- 
2.14.4

[Qemu-devel] [PATCH 1/3] qemu-error: add {error, warn}_report_once_cond

[Cornelia Huck]

Add two functions to print an error/warning report once depending
on a passed-in condition variable and flip it if printed. This is
useful if you want to print a message not once-globally, but e.g.
once-per-device.

Inspired by warn_once() in hw/vfio/ccw.c.

Signed-off-by: Cornelia Huck <cohuck@redhat.com>
---
 include/qemu/error-report.h |  5 +++++
 util/qemu-error.c           | 44 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+)

diff --git a/include/qemu/error-report.h b/include/qemu/error-report.h
index 72fab2b031..d2a6515e68 100644
--- a/include/qemu/error-report.h
+++ b/include/qemu/error-report.h
@@ -44,6 +44,11 @@ void error_report(const char *fmt, ...) GCC_FMT_ATTR(1, 2);
 void warn_report(const char *fmt, ...) GCC_FMT_ATTR(1, 2);
 void info_report(const char *fmt, ...) GCC_FMT_ATTR(1, 2);
 
+void error_report_once_cond(bool *printed, const char *fmt, ...)
+    GCC_FMT_ATTR(2, 3);
+void warn_report_once_cond(bool *printed, const char *fmt, ...)
+    GCC_FMT_ATTR(2, 3);
+
 /*
  * Similar to error_report(), except it prints the message just once.
  * Return true when it prints, false otherwise.
diff --git a/util/qemu-error.c b/util/qemu-error.c
index a25d3b94c6..0894ab6995 100644
--- a/util/qemu-error.c
+++ b/util/qemu-error.c
@@ -310,3 +310,47 @@ void info_report(const char *fmt, ...)
     vreport(REPORT_TYPE_INFO, fmt, ap);
     va_end(ap);
 }
+
+/*
+ * If *printed is false, print an error message to current monitor if we
+ * have one, else to stderr, and flip *printed to true.
+ * If printed is NULL, do not print anything.
+ * Format arguments like sprintf().  The resulting message should be
+ * a single phrase, with no newline or trailing punctuation.
+ * Prepend the current location and append a newline.
+ * It's wrong to call this in a QMP monitor.  Use error_setg() there.
+ */
+void error_report_once_cond(bool *printed, const char *fmt, ...)
+{
+    va_list ap;
+
+    if (!printed || *printed) {
+        return;
+    }
+    *printed = true;
+    va_start(ap, fmt);
+    vreport(REPORT_TYPE_ERROR, fmt, ap);
+    va_end(ap);
+}
+
+/*
+ * If *printed is false, print a warning message to current monitor if we
+ * have one, else to stderr, and flip *printed to true.
+ * If printed is NULL, do not print anything.
+ * Format arguments like sprintf().  The resulting message should be
+ * a single phrase, with no newline or trailing punctuation.
+ * Prepend the current location and append a newline.
+ * It's wrong to call this in a QMP monitor.  Use error_setg() there.
+ */
+void warn_report_once_cond(bool *printed, const char *fmt, ...)
+{
+    va_list ap;
+
+    if (!printed || *printed) {
+        return;
+    }
+    *printed = true;
+    va_start(ap, fmt);
+    vreport(REPORT_TYPE_WARNING, fmt, ap);
+    va_end(ap);
+}
-- 
2.14.4

[Qemu-devel] [PATCH 2/3] qemu-error: make use of {error, warn}_report_once_cond

[Cornelia Huck]

{error,warn}_report_once() are a special case of the new functions
and can simply switch to them.

Signed-off-by: Cornelia Huck <cohuck@redhat.com>
---
 include/qemu/error-report.h | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/include/qemu/error-report.h b/include/qemu/error-report.h
index d2a6515e68..4e4c0e757c 100644
--- a/include/qemu/error-report.h
+++ b/include/qemu/error-report.h
@@ -58,10 +58,7 @@ void warn_report_once_cond(bool *printed, const char *fmt, ...)
         static bool print_once_;                \
         bool ret_print_once_ = !print_once_;    \
                                                 \
-        if (!print_once_) {                     \
-            print_once_ = true;                 \
-            error_report(fmt, ##__VA_ARGS__);   \
-        }                                       \
+        error_report_once_cond(&print_once_, fmt, ##__VA_ARGS__); \
         unlikely(ret_print_once_);              \
     })
 
@@ -74,10 +71,7 @@ void warn_report_once_cond(bool *printed, const char *fmt, ...)
         static bool print_once_;                \
         bool ret_print_once_ = !print_once_;    \
                                                 \
-        if (!print_once_) {                     \
-            print_once_ = true;                 \
-            warn_report(fmt, ##__VA_ARGS__);    \
-        }                                       \
+        warn_report_once_cond(&print_once_, fmt, ##__VA_ARGS__); \
         unlikely(ret_print_once_);              \
     })
 
-- 
2.14.4

[Qemu-devel] [PATCH 3/3] vfio-ccw: switch to warn_report_once_cond()

[Cornelia Huck]

We can replace the local function with the new common interface.

Signed-off-by: Cornelia Huck <cohuck@redhat.com>
---
 hw/vfio/ccw.c | 18 +++---------------
 1 file changed, 3 insertions(+), 15 deletions(-)

diff --git a/hw/vfio/ccw.c b/hw/vfio/ccw.c
index e96bbdc78b..9246729a75 100644
--- a/hw/vfio/ccw.c
+++ b/hw/vfio/ccw.c
@@ -37,24 +37,12 @@ typedef struct VFIOCCWDevice {
     bool warned_orb_pfch;
 } VFIOCCWDevice;
 
-static inline void warn_once(bool *warned, const char *fmt, ...)
-{
-    va_list ap;
-
-    if (!warned || *warned) {
-        return;
-    }
-    *warned = true;
-    va_start(ap, fmt);
-    warn_vreport(fmt, ap);
-    va_end(ap);
-}
-
 static inline void warn_once_pfch(VFIOCCWDevice *vcdev, SubchDev *sch,
                                   const char *msg)
 {
-    warn_once(&vcdev->warned_orb_pfch, "vfio-ccw (devno %x.%x.%04x): %s",
-              sch->cssid, sch->ssid, sch->devno, msg);
+    warn_report_once_cond(&vcdev->warned_orb_pfch,
+                          "vfio-ccw (devno %x.%x.%04x): %s",
+                          sch->cssid, sch->ssid, sch->devno, msg);
 }
 
 static void vfio_ccw_compute_needs_reset(VFIODevice *vdev)
-- 
2.14.4

Re: [Qemu-devel] [PATCH 1/3] qemu-error: add {error, warn}_report_once_cond

[Markus Armbruster]

Cornelia Huck <cohuck@redhat.com> writes:

> Add two functions to print an error/warning report once depending
> on a passed-in condition variable and flip it if printed. This is
> useful if you want to print a message not once-globally, but e.g.
> once-per-device.
>
> Inspired by warn_once() in hw/vfio/ccw.c.

This leaves the reader wondering why you don't replace that function.
You do, in PATCH 3.  I'd either announce that here, or squash the two
patches.

>
> Signed-off-by: Cornelia Huck <cohuck@redhat.com>
> ---
>  include/qemu/error-report.h |  5 +++++
>  util/qemu-error.c           | 44 ++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 49 insertions(+)
>
> diff --git a/include/qemu/error-report.h b/include/qemu/error-report.h
> index 72fab2b031..d2a6515e68 100644
> --- a/include/qemu/error-report.h
> +++ b/include/qemu/error-report.h
> @@ -44,6 +44,11 @@ void error_report(const char *fmt, ...) GCC_FMT_ATTR(1, 2);
>  void warn_report(const char *fmt, ...) GCC_FMT_ATTR(1, 2);
>  void info_report(const char *fmt, ...) GCC_FMT_ATTR(1, 2);
>  
> +void error_report_once_cond(bool *printed, const char *fmt, ...)
> +    GCC_FMT_ATTR(2, 3);
> +void warn_report_once_cond(bool *printed, const char *fmt, ...)
> +    GCC_FMT_ATTR(2, 3);
> +
>  /*
>   * Similar to error_report(), except it prints the message just once.
>   * Return true when it prints, false otherwise.
> diff --git a/util/qemu-error.c b/util/qemu-error.c
> index a25d3b94c6..0894ab6995 100644
> --- a/util/qemu-error.c
> +++ b/util/qemu-error.c
> @@ -310,3 +310,47 @@ void info_report(const char *fmt, ...)
>      vreport(REPORT_TYPE_INFO, fmt, ap);
>      va_end(ap);
>  }
> +
> +/*
> + * If *printed is false, print an error message to current monitor if we
> + * have one, else to stderr, and flip *printed to true.
> + * If printed is NULL, do not print anything.

Any particular reason for supporting null @printed?

For what it's worth, warn_once() supports it, but its caller doesn't use
it.

> + * Format arguments like sprintf().  The resulting message should be
> + * a single phrase, with no newline or trailing punctuation.
> + * Prepend the current location and append a newline.
> + * It's wrong to call this in a QMP monitor.  Use error_setg() there.
> + */
> +void error_report_once_cond(bool *printed, const char *fmt, ...)
> +{
> +    va_list ap;
> +
> +    if (!printed || *printed) {
> +        return;
> +    }
> +    *printed = true;
> +    va_start(ap, fmt);
> +    vreport(REPORT_TYPE_ERROR, fmt, ap);
> +    va_end(ap);
> +}
> +
> +/*
> + * If *printed is false, print a warning message to current monitor if we
> + * have one, else to stderr, and flip *printed to true.
> + * If printed is NULL, do not print anything.
> + * Format arguments like sprintf().  The resulting message should be
> + * a single phrase, with no newline or trailing punctuation.
> + * Prepend the current location and append a newline.
> + * It's wrong to call this in a QMP monitor.  Use error_setg() there.
> + */
> +void warn_report_once_cond(bool *printed, const char *fmt, ...)
> +{
> +    va_list ap;
> +
> +    if (!printed || *printed) {
> +        return;
> +    }
> +    *printed = true;
> +    va_start(ap, fmt);
> +    vreport(REPORT_TYPE_WARNING, fmt, ap);
> +    va_end(ap);
> +}

Re: [Qemu-devel] [PATCH 2/3] qemu-error: make use of {error, warn}_report_once_cond

[Markus Armbruster]

Cornelia Huck <cohuck@redhat.com> writes:

> {error,warn}_report_once() are a special case of the new functions
> and can simply switch to them.
>
> Signed-off-by: Cornelia Huck <cohuck@redhat.com>
> ---
>  include/qemu/error-report.h | 10 ++--------
>  1 file changed, 2 insertions(+), 8 deletions(-)
>
> diff --git a/include/qemu/error-report.h b/include/qemu/error-report.h
> index d2a6515e68..4e4c0e757c 100644
> --- a/include/qemu/error-report.h
> +++ b/include/qemu/error-report.h
> @@ -58,10 +58,7 @@ void warn_report_once_cond(bool *printed, const char *fmt, ...)
>          static bool print_once_;                \
>          bool ret_print_once_ = !print_once_;    \
>                                                  \
> -        if (!print_once_) {                     \
> -            print_once_ = true;                 \
> -            error_report(fmt, ##__VA_ARGS__);   \
> -        }                                       \
> +        error_report_once_cond(&print_once_, fmt, ##__VA_ARGS__); \
>          unlikely(ret_print_once_);              \
>      })
>  
> @@ -74,10 +71,7 @@ void warn_report_once_cond(bool *printed, const char *fmt, ...)
>          static bool print_once_;                \
>          bool ret_print_once_ = !print_once_;    \
>                                                  \
> -        if (!print_once_) {                     \
> -            print_once_ = true;                 \
> -            warn_report(fmt, ##__VA_ARGS__);    \
> -        }                                       \
> +        warn_report_once_cond(&print_once_, fmt, ##__VA_ARGS__); \
>          unlikely(ret_print_once_);              \
>      })

Hmm.  The macros return a value, while the functions do not.  Doesn't
this contradict the commit message's claim the macros are ä special case
of the new functions"?

If you make the functions return the value, too, the macros become
simpler.  Moving complexity from macros to functions feels like a good
deal, even when it's just a little bit of complexity like here.

Re: [Qemu-devel] [PATCH 1/3] qemu-error: add {error, warn}_report_once_cond

[Cornelia Huck]

On Wed, 29 Aug 2018 18:07:46 +0200
Markus Armbruster <armbru@redhat.com> wrote:

> Cornelia Huck <cohuck@redhat.com> writes:
> 
> > Add two functions to print an error/warning report once depending
> > on a passed-in condition variable and flip it if printed. This is
> > useful if you want to print a message not once-globally, but e.g.
> > once-per-device.
> >
> > Inspired by warn_once() in hw/vfio/ccw.c.  
> 
> This leaves the reader wondering why you don't replace that function.
> You do, in PATCH 3.  I'd either announce that here, or squash the two
> patches.

Squashing probably makes the most sense.

> 
> >
> > Signed-off-by: Cornelia Huck <cohuck@redhat.com>
> > ---
> >  include/qemu/error-report.h |  5 +++++
> >  util/qemu-error.c           | 44 ++++++++++++++++++++++++++++++++++++++++++++
> >  2 files changed, 49 insertions(+)
> >
> > diff --git a/include/qemu/error-report.h b/include/qemu/error-report.h
> > index 72fab2b031..d2a6515e68 100644
> > --- a/include/qemu/error-report.h
> > +++ b/include/qemu/error-report.h
> > @@ -44,6 +44,11 @@ void error_report(const char *fmt, ...) GCC_FMT_ATTR(1, 2);
> >  void warn_report(const char *fmt, ...) GCC_FMT_ATTR(1, 2);
> >  void info_report(const char *fmt, ...) GCC_FMT_ATTR(1, 2);
> >  
> > +void error_report_once_cond(bool *printed, const char *fmt, ...)
> > +    GCC_FMT_ATTR(2, 3);
> > +void warn_report_once_cond(bool *printed, const char *fmt, ...)
> > +    GCC_FMT_ATTR(2, 3);
> > +
> >  /*
> >   * Similar to error_report(), except it prints the message just once.
> >   * Return true when it prints, false otherwise.
> > diff --git a/util/qemu-error.c b/util/qemu-error.c
> > index a25d3b94c6..0894ab6995 100644
> > --- a/util/qemu-error.c
> > +++ b/util/qemu-error.c
> > @@ -310,3 +310,47 @@ void info_report(const char *fmt, ...)
> >      vreport(REPORT_TYPE_INFO, fmt, ap);
> >      va_end(ap);
> >  }
> > +
> > +/*
> > + * If *printed is false, print an error message to current monitor if we
> > + * have one, else to stderr, and flip *printed to true.
> > + * If printed is NULL, do not print anything.  
> 
> Any particular reason for supporting null @printed?
> 
> For what it's worth, warn_once() supports it, but its caller doesn't use
> it.

I can change this to asserting on NULL @printed. If you call this with
NULL, you probably have messed up somewhere already.

> 
> > + * Format arguments like sprintf().  The resulting message should be
> > + * a single phrase, with no newline or trailing punctuation.
> > + * Prepend the current location and append a newline.
> > + * It's wrong to call this in a QMP monitor.  Use error_setg() there.
> > + */
> > +void error_report_once_cond(bool *printed, const char *fmt, ...)
> > +{
> > +    va_list ap;
> > +
> > +    if (!printed || *printed) {
> > +        return;
> > +    }
> > +    *printed = true;
> > +    va_start(ap, fmt);
> > +    vreport(REPORT_TYPE_ERROR, fmt, ap);
> > +    va_end(ap);
> > +}
> > +
> > +/*
> > + * If *printed is false, print a warning message to current monitor if we
> > + * have one, else to stderr, and flip *printed to true.
> > + * If printed is NULL, do not print anything.
> > + * Format arguments like sprintf().  The resulting message should be
> > + * a single phrase, with no newline or trailing punctuation.
> > + * Prepend the current location and append a newline.
> > + * It's wrong to call this in a QMP monitor.  Use error_setg() there.
> > + */
> > +void warn_report_once_cond(bool *printed, const char *fmt, ...)
> > +{
> > +    va_list ap;
> > +
> > +    if (!printed || *printed) {
> > +        return;
> > +    }
> > +    *printed = true;
> > +    va_start(ap, fmt);
> > +    vreport(REPORT_TYPE_WARNING, fmt, ap);
> > +    va_end(ap);
> > +}  

Re: [Qemu-devel] [PATCH 2/3] qemu-error: make use of {error, warn}_report_once_cond

[Cornelia Huck]

On Wed, 29 Aug 2018 18:12:32 +0200
Markus Armbruster <armbru@redhat.com> wrote:

> Cornelia Huck <cohuck@redhat.com> writes:
> 
> > {error,warn}_report_once() are a special case of the new functions
> > and can simply switch to them.
> >
> > Signed-off-by: Cornelia Huck <cohuck@redhat.com>
> > ---
> >  include/qemu/error-report.h | 10 ++--------
> >  1 file changed, 2 insertions(+), 8 deletions(-)
> >
> > diff --git a/include/qemu/error-report.h b/include/qemu/error-report.h
> > index d2a6515e68..4e4c0e757c 100644
> > --- a/include/qemu/error-report.h
> > +++ b/include/qemu/error-report.h
> > @@ -58,10 +58,7 @@ void warn_report_once_cond(bool *printed, const char *fmt, ...)
> >          static bool print_once_;                \
> >          bool ret_print_once_ = !print_once_;    \
> >                                                  \
> > -        if (!print_once_) {                     \
> > -            print_once_ = true;                 \
> > -            error_report(fmt, ##__VA_ARGS__);   \
> > -        }                                       \
> > +        error_report_once_cond(&print_once_, fmt, ##__VA_ARGS__); \
> >          unlikely(ret_print_once_);              \
> >      })
> >  
> > @@ -74,10 +71,7 @@ void warn_report_once_cond(bool *printed, const char *fmt, ...)
> >          static bool print_once_;                \
> >          bool ret_print_once_ = !print_once_;    \
> >                                                  \
> > -        if (!print_once_) {                     \
> > -            print_once_ = true;                 \
> > -            warn_report(fmt, ##__VA_ARGS__);    \
> > -        }                                       \
> > +        warn_report_once_cond(&print_once_, fmt, ##__VA_ARGS__); \
> >          unlikely(ret_print_once_);              \
> >      })  
> 
> Hmm.  The macros return a value, while the functions do not.  Doesn't
> this contradict the commit message's claim the macros are ä special case
> of the new functions"?
> 
> If you make the functions return the value, too, the macros become
> simpler.  Moving complexity from macros to functions feels like a good
> deal, even when it's just a little bit of complexity like here.

Reducing macro complexity is a good idea, agreed.

Thanks for looking!

Re: [Qemu-devel] [PATCH 0/3] qemu-error: advanced report_once handling

[Markus Armbruster]

Cornelia Huck <cohuck@redhat.com> writes:

> Based on previous discussions, I wanted to enhance the recently
> merged report_once infrastucture with a way to print a message
> once based on a variable instead of globally-once, similar to
> what vfio-ccw uses today.
>
> Not really tested, mainly wanted to get this out before my vacation
> to get the ball rolling.

I had a few comments, but found nothing serious enough to withhold my
Reviewed-by: Markus Armbruster <armbru@redhat.com>