[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[Xen-devel] [RFC v5 024/126] error: auto propagated local_err



Here is introduced ERRP_AUTO_PROPAGATE macro, to be used at start of
functions with errp OUT parameter.

It has three goals:

1. Fix issue with error_fatal & error_prepend/error_append_hint: user
can't see this additional information, because exit() happens in
error_setg earlier than information is added. [Reported by Greg Kurz]

2. Fix issue with error_abort & error_propagate: when we wrap
error_abort by local_err+error_propagate, resulting coredump will
refer to error_propagate and not to the place where error happened.
(the macro itself doesn't fix the issue, but it allows to [3.] drop all
local_err+error_propagate pattern, which will definitely fix the issue)
[Reported by Kevin Wolf]

3. Drop local_err+error_propagate pattern, which is used to workaround
void functions with errp parameter, when caller wants to know resulting
status. (Note: actually these functions could be merely updated to
return int error code).

To achieve these goals, we need to add invocation of the macro at start
of functions, which needs error_prepend/error_append_hint (1.); add
invocation of the macro at start of functions which do
local_err+error_propagate scenario the check errors, drop local errors
from them and just use *errp instead (2., 3.).

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@xxxxxxxxxxxxx>
Reviewed-by: Eric Blake <eblake@xxxxxxxxxx>
---

CC: Gerd Hoffmann <kraxel@xxxxxxxxxx>
CC: "Gonglei (Arei)" <arei.gonglei@xxxxxxxxxx>
CC: Eduardo Habkost <ehabkost@xxxxxxxxxx>
CC: Igor Mammedov <imammedo@xxxxxxxxxx>
CC: Laurent Vivier <lvivier@xxxxxxxxxx>
CC: Amit Shah <amit@xxxxxxxxxx>
CC: Kevin Wolf <kwolf@xxxxxxxxxx>
CC: Max Reitz <mreitz@xxxxxxxxxx>
CC: John Snow <jsnow@xxxxxxxxxx>
CC: Ari Sundholm <ari@xxxxxxxxxx>
CC: Pavel Dovgalyuk <pavel.dovgaluk@xxxxxxxxx>
CC: Paolo Bonzini <pbonzini@xxxxxxxxxx>
CC: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
CC: Fam Zheng <fam@xxxxxxxxxx>
CC: Stefan Weil <sw@xxxxxxxxxxx>
CC: Ronnie Sahlberg <ronniesahlberg@xxxxxxxxx>
CC: Peter Lieven <pl@xxxxxxx>
CC: Eric Blake <eblake@xxxxxxxxxx>
CC: "Denis V. Lunev" <den@xxxxxxxxxx>
CC: Markus Armbruster <armbru@xxxxxxxxxx>
CC: Alberto Garcia <berto@xxxxxxxxxx>
CC: Jason Dillaman <dillaman@xxxxxxxxxx>
CC: Wen Congyang <wencongyang2@xxxxxxxxxx>
CC: Xie Changlong <xiechanglong.d@xxxxxxxxx>
CC: Liu Yuan <namei.unix@xxxxxxxxx>
CC: "Richard W.M. Jones" <rjones@xxxxxxxxxx>
CC: Jeff Cody <codyprime@xxxxxxxxx>
CC: "Marc-André Lureau" <marcandre.lureau@xxxxxxxxxx>
CC: "Daniel P. Berrangé" <berrange@xxxxxxxxxx>
CC: Richard Henderson <rth@xxxxxxxxxxx>
CC: Greg Kurz <groug@xxxxxxxx>
CC: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
CC: Marcel Apfelbaum <marcel.apfelbaum@xxxxxxxxx>
CC: Beniamino Galvani <b.galvani@xxxxxxxxx>
CC: Peter Maydell <peter.maydell@xxxxxxxxxx>
CC: "Cédric Le Goater" <clg@xxxxxxxx>
CC: Andrew Jeffery <andrew@xxxxxxxx>
CC: Joel Stanley <joel@xxxxxxxxx>
CC: Andrew Baumann <Andrew.Baumann@xxxxxxxxxxxxx>
CC: "Philippe Mathieu-Daudé" <philmd@xxxxxxxxxx>
CC: Antony Pavlov <antonynpavlov@xxxxxxxxx>
CC: Jean-Christophe Dubois <jcd@xxxxxxxxxxxxxxx>
CC: Peter Chubb <peter.chubb@xxxxxxxxxxxx>
CC: Subbaraya Sundeep <sundeep.lkml@xxxxxxxxx>
CC: Eric Auger <eric.auger@xxxxxxxxxx>
CC: Alistair Francis <alistair@xxxxxxxxxxxxx>
CC: "Edgar E. Iglesias" <edgar.iglesias@xxxxxxxxx>
CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
CC: Anthony Perard <anthony.perard@xxxxxxxxxx>
CC: Paul Durrant <paul@xxxxxxx>
CC: Paul Burton <pburton@xxxxxxxxxxxx>
CC: Aleksandar Rikalo <arikalo@xxxxxxxxxxxx>
CC: Chris Wulff <crwulff@xxxxxxxxx>
CC: Marek Vasut <marex@xxxxxxx>
CC: David Gibson <david@xxxxxxxxxxxxxxxxxxxxx>
CC: Cornelia Huck <cohuck@xxxxxxxxxx>
CC: Halil Pasic <pasic@xxxxxxxxxxxxx>
CC: Christian Borntraeger <borntraeger@xxxxxxxxxx>
CC: "Hervé Poussineau" <hpoussin@xxxxxxxxxxx>
CC: Xiao Guangrong <xiaoguangrong.eric@xxxxxxxxx>
CC: Aurelien Jarno <aurelien@xxxxxxxxxxx>
CC: Aleksandar Markovic <amarkovic@xxxxxxxxxxxx>
CC: Mark Cave-Ayland <mark.cave-ayland@xxxxxxxxxxxx>
CC: Jason Wang <jasowang@xxxxxxxxxx>
CC: Laszlo Ersek <lersek@xxxxxxxxxx>
CC: Yuval Shaia <yuval.shaia@xxxxxxxxxx>
CC: Palmer Dabbelt <palmer@xxxxxxxxxx>
CC: Sagar Karandikar <sagark@xxxxxxxxxxxxxxxxx>
CC: Bastian Koppelmann <kbastian@xxxxxxxxxxxxxxxxxxxxx>
CC: David Hildenbrand <david@xxxxxxxxxx>
CC: Thomas Huth <thuth@xxxxxxxxxx>
CC: Eric Farman <farman@xxxxxxxxxxxxx>
CC: Matthew Rosato <mjrosato@xxxxxxxxxxxxx>
CC: Hannes Reinecke <hare@xxxxxxxx>
CC: Michael Walle <michael@xxxxxxxx>
CC: Artyom Tarasenko <atar4qemu@xxxxxxxxx>
CC: Stefan Berger <stefanb@xxxxxxxxxxxxx>
CC: Samuel Thibault <samuel.thibault@xxxxxxxxxxxx>
CC: Alex Williamson <alex.williamson@xxxxxxxxxx>
CC: Tony Krowiak <akrowiak@xxxxxxxxxxxxx>
CC: Pierre Morel <pmorel@xxxxxxxxxxxxx>
CC: Michael Roth <mdroth@xxxxxxxxxxxxxxxxxx>
CC: Hailiang Zhang <zhang.zhanghailiang@xxxxxxxxxx>
CC: Juan Quintela <quintela@xxxxxxxxxx>
CC: "Dr. David Alan Gilbert" <dgilbert@xxxxxxxxxx>
CC: Luigi Rizzo <rizzo@xxxxxxxxxxxx>
CC: Giuseppe Lettieri <g.lettieri@xxxxxxxxxxxx>
CC: Vincenzo Maffione <v.maffione@xxxxxxxxx>
CC: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
CC: Anthony Green <green@xxxxxxxxxxxxxx>
CC: Stafford Horne <shorne@xxxxxxxxx>
CC: Guan Xuetao <gxt@xxxxxxxxxxxxxxx>
CC: Max Filippov <jcmvbkbc@xxxxxxxxx>
CC: qemu-block@xxxxxxxxxx
CC: integration@xxxxxxxxxxx
CC: sheepdog@xxxxxxxxxxxxxx
CC: qemu-arm@xxxxxxxxxx
CC: xen-devel@xxxxxxxxxxxxxxxxxxxx
CC: qemu-ppc@xxxxxxxxxx
CC: qemu-s390x@xxxxxxxxxx
CC: qemu-riscv@xxxxxxxxxx

 include/qapi/error.h | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/include/qapi/error.h b/include/qapi/error.h
index d6898d833b..47238d9065 100644
--- a/include/qapi/error.h
+++ b/include/qapi/error.h
@@ -345,6 +345,44 @@ void error_set_internal(Error **errp,
                         ErrorClass err_class, const char *fmt, ...)
     GCC_FMT_ATTR(6, 7);
 
+typedef struct ErrorPropagator {
+    Error *local_err;
+    Error **errp;
+} ErrorPropagator;
+
+static inline void error_propagator_cleanup(ErrorPropagator *prop)
+{
+    error_propagate(prop->errp, prop->local_err);
+}
+
+G_DEFINE_AUTO_CLEANUP_CLEAR_FUNC(ErrorPropagator, error_propagator_cleanup);
+
+/*
+ * ERRP_AUTO_PROPAGATE
+ *
+ * This macro is created to be the first line of a function with Error **errp
+ * OUT parameter. It's needed only in cases where we want to use error_prepend,
+ * error_append_hint or dereference *errp. It's still safe (but useless) in
+ * other cases.
+ *
+ * If errp is NULL or points to error_fatal, it is rewritten to point to a
+ * local Error object, which will be automatically propagated to the original
+ * errp on function exit (see error_propagator_cleanup).
+ *
+ * After invocation of this macro it is always safe to dereference errp
+ * (as it's not NULL anymore) and to add information (by error_prepend or
+ * error_append_hint)
+ * (as, if it was error_fatal, we swapped it with a local_error to be
+ * propagated on cleanup).
+ *
+ * Note: we don't wrap the error_abort case, as we want resulting coredump
+ * to point to the place where the error happened, not to error_propagate.
+ */
+#define ERRP_AUTO_PROPAGATE()                                  \
+    g_auto(ErrorPropagator) _auto_errp_prop = {.errp = errp};  \
+    errp = ((errp == NULL || *errp == error_fatal)             \
+            ? &_auto_errp_prop.local_err : errp)
+
 /*
  * Special error destination to abort on error.
  * See error_setg() and error_propagate() for details.
-- 
2.21.0


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel

 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.