On 05/22/2018 10:18 PM, Peter Xu wrote:
I stole the printk_once() macro.
I always wanted to be able to print some error directly if there is a
buffer to dump, however we can't use error_report() where the code path
can be triggered by DDOS attack. To avoid that, we can introduce a
print-once-like function for it. Meanwhile, we also introduce the
corresponding helper for warn_report().
CC: Markus Armbruster <arm...@redhat.com>
Signed-off-by: Peter Xu <pet...@redhat.com>
---
include/qemu/error-report.h | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
diff --git a/include/qemu/error-report.h b/include/qemu/error-report.h
index e1c8ae1a52..3e6e84801f 100644
--- a/include/qemu/error-report.h
+++ b/include/qemu/error-report.h
@@ -44,6 +44,32 @@ 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);
+/* Similar to error_report(), but it only prints the message once. */
+#define error_report_once(fmt, ...) \
+ ({ \
+ static bool __print_once; \
+ bool __ret_print_once = !__print_once; \
In v1 you were asked to avoid leading double underscore
(https://lists.gnu.org/archive/html/qemu-devel/2018-05/msg03442.html;
use things like 'print_once_' instead) and to document the return value
of these macros
(https://lists.gnu.org/archive/html/qemu-devel/2018-05/msg03503.html;
having the return value makes it possible to write conditional code that
caches further information about a first, but not repeat, failures).
Why hasn't that happened?
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
