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Tue, 26 Aug 2025 11:40:39 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.174]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 0D2C81955F24; Tue, 26 Aug 2025 11:40:36 +0000 (UTC) Date: Tue, 26 Aug 2025 12:40:33 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Paolo Bonzini Cc: qemu-devel@nongnu.org, tanishdesai37@gmail.com, stefanha@redhat.com, mads@ynddal.dk Subject: Re: [PATCH 03/14] trace/ftrace: move snprintf+write from tracepoints to ftrace.c Message-ID: References: <20250822122655.1353197-1-pbonzini@redhat.com> <20250822122655.1353197-4-pbonzini@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20250822122655.1353197-4-pbonzini@redhat.com> User-Agent: Mutt/2.2.14 (2025-02-20) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Fri, Aug 22, 2025 at 02:26:44PM +0200, Paolo Bonzini wrote: > This simplifies the Python code and reduces the size of the tracepoints. > > Signed-off-by: Paolo Bonzini > --- > tests/tracetool/ftrace.h | 28 ++++++---------------------- > trace/ftrace.h | 1 + > trace/ftrace.c | 15 +++++++++++++++ > scripts/tracetool/backend/ftrace.py | 12 ++---------- > 4 files changed, 24 insertions(+), 32 deletions(-) > > diff --git a/tests/tracetool/ftrace.h b/tests/tracetool/ftrace.h > index fe22ea0f09f..1dfe4239413 100644 > --- a/tests/tracetool/ftrace.h > +++ b/tests/tracetool/ftrace.h > @@ -21,18 +21,10 @@ extern uint16_t _TRACE_TEST_WIBBLE_DSTATE; > > static inline void trace_test_blah(void *context, const char *filename) > { > - { > - char ftrace_buf[MAX_TRACE_STRLEN]; > - int unused __attribute__ ((unused)); > - int trlen; > - if (trace_event_get_state(TRACE_TEST_BLAH)) { > + if (trace_event_get_state(TRACE_TEST_BLAH)) { > #line 4 "trace-events" > - trlen = snprintf(ftrace_buf, MAX_TRACE_STRLEN, > - "test_blah " "Blah context=%p filename=%s" "\n" , context, filename); > -#line 33 "ftrace.h" > - trlen = MIN(trlen, MAX_TRACE_STRLEN - 1); > - unused = write(trace_marker_fd, ftrace_buf, trlen); > - } > + ftrace_write("test_blah " "Blah context=%p filename=%s" "\n" , context, filename); > +#line 28 "ftrace.h" > } > } > > @@ -42,18 +34,10 @@ static inline void trace_test_blah(void *context, const char *filename) > > static inline void trace_test_wibble(void *context, int value) > { > - { > - char ftrace_buf[MAX_TRACE_STRLEN]; > - int unused __attribute__ ((unused)); > - int trlen; > - if (trace_event_get_state(TRACE_TEST_WIBBLE)) { > + if (trace_event_get_state(TRACE_TEST_WIBBLE)) { > #line 5 "trace-events" > - trlen = snprintf(ftrace_buf, MAX_TRACE_STRLEN, > - "test_wibble " "Wibble context=%p value=%d" "\n" , context, value); > -#line 54 "ftrace.h" > - trlen = MIN(trlen, MAX_TRACE_STRLEN - 1); > - unused = write(trace_marker_fd, ftrace_buf, trlen); > - } > + ftrace_write("test_wibble " "Wibble context=%p value=%d" "\n" , context, value); > +#line 41 "ftrace.h" > } > } > #endif /* TRACE_TESTSUITE_GENERATED_TRACERS_H */ snip > diff --git a/trace/ftrace.c b/trace/ftrace.c > index 9749543d9b2..6875faedb9c 100644 > --- a/trace/ftrace.c > +++ b/trace/ftrace.c > @@ -38,6 +38,21 @@ static int find_mount(char *mount_point, const char *fstype) > return ret; > } > > +void ftrace_write(const char *fmt, ...) > +{ > + char ftrace_buf[MAX_TRACE_STRLEN]; > + int unused __attribute__ ((unused)); > + int trlen; > + va_list ap; > + > + va_start(ap, fmt); > + trlen = vsnprintf(ftrace_buf, MAX_TRACE_STRLEN, fmt, ap); > + va_end(ap); > + > + trlen = MIN(trlen, MAX_TRACE_STRLEN - 1); > + unused = write(trace_marker_fd, ftrace_buf, trlen); You're just copying the existing code pattern which is fine for now so Reviewed-by: Daniel P. Berrangé More generally though, IMHO, QEMU would be better off bringing in gnulib's 'ignore_value' macro, but simplified since we don't care about ancient GCC #define ignore_value(x) \ (__extension__ ({ __typeof__ (x) __x = (x); (void) __x; })) so that we don't need to play games with extra variables. eg ignore_value(write(trace_marker_fd, ftrace_buf, trlen)); With regards, Daniel [1] https://github.com/coreutils/gnulib/blob/master/lib/ignore-value.h#L38 -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|