| Message ID | 20190208134918.5618-4-tstoyanov@vmware.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | trace-cmd: Timetamps sync using PTP-like algorithm, relying on vsock events. | expand |
On Fri, 8 Feb 2019 15:49:14 +0200 Tzvetomir Stoyanov <tstoyanov@vmware.com> wrote: > Fixed the logic in tracecmd_read_page_record() when > searching for the next event in the event from the > ring buffer. In the current logic, in the case when > last_record is not NULL (we are searching for the second one) > the check "if (ptr != last_record->data)" always fails. > Nice catch. Let's change the change log and subject: Subject trace-cmd: Fix tracecmd_read_page_record() to read more than one event The kbuffer_next_event() will return the next event on the sub buffer. If we pass in the last_record to tracecmd_read_page_record(), it initializes the sub buffer, and by calling kbuffer_next_event() (instead of kbuffer_read_event()), the second event on the sub buffer is returned. This causes the match of the last_record not to match if the last_record happens to be the first event on the sub buffer. > Signed-off-by: Tzvetomir Stoyanov <tstoyanov@vmware.com> > --- > lib/trace-cmd/trace-input.c | 12 ++++++++---- > 1 file changed, 8 insertions(+), 4 deletions(-) > > diff --git a/lib/trace-cmd/trace-input.c b/lib/trace-cmd/trace-input.c > index 33ad7d1..5d64ca8 100644 > --- a/lib/trace-cmd/trace-input.c > +++ b/lib/trace-cmd/trace-input.c > @@ -1688,18 +1688,22 @@ tracecmd_read_page_record(struct tep_handle *pevent, void *page, int size, > goto out_free; > } > > - do { > + ptr = kbuffer_read_event(kbuf, &ts); > + while (ptr < last_record->data) { > ptr = kbuffer_next_event(kbuf, NULL); > if (!ptr) > break; > - } while (ptr < last_record->data); > + if (ptr == last_record->data) > + break; > + } > if (ptr != last_record->data) { > warning("tracecmd_read_page_record: could not find last_record"); > goto out_free; > } > - } > + ptr = kbuffer_next_event(kbuf, &ts); > + } else > + ptr = kbuffer_read_event(kbuf, &ts); > > - ptr = kbuffer_read_event(kbuf, &ts); Also, instead of the above "} else" clause, we can just move the ptr = kbuffer_read_event(kbuf, &ts); before the if condition testing last_record. -- Steve > if (!ptr) > goto out_free; >
diff --git a/lib/trace-cmd/trace-input.c b/lib/trace-cmd/trace-input.c index 33ad7d1..5d64ca8 100644 --- a/lib/trace-cmd/trace-input.c +++ b/lib/trace-cmd/trace-input.c @@ -1688,18 +1688,22 @@ tracecmd_read_page_record(struct tep_handle *pevent, void *page, int size, goto out_free; } - do { + ptr = kbuffer_read_event(kbuf, &ts); + while (ptr < last_record->data) { ptr = kbuffer_next_event(kbuf, NULL); if (!ptr) break; - } while (ptr < last_record->data); + if (ptr == last_record->data) + break; + } if (ptr != last_record->data) { warning("tracecmd_read_page_record: could not find last_record"); goto out_free; } - } + ptr = kbuffer_next_event(kbuf, &ts); + } else + ptr = kbuffer_read_event(kbuf, &ts); - ptr = kbuffer_read_event(kbuf, &ts); if (!ptr) goto out_free;
Fixed the logic in tracecmd_read_page_record() when searching for the next event in the event from the ring buffer. In the current logic, in the case when last_record is not NULL (we are searching for the second one) the check "if (ptr != last_record->data)" always fails. Signed-off-by: Tzvetomir Stoyanov <tstoyanov@vmware.com> --- lib/trace-cmd/trace-input.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-)