From: Jérémie Galarneau Date: Fri, 12 Mar 2021 19:54:52 +0000 (-0500) Subject: Fix: sessiond: off-by-one poll check when draining an event notifier X-Git-Tag: v2.13.0-rc1~243 X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=a17b133bc868e046f285146e26a5bbe2a569b892;p=lttng-tools.git Fix: sessiond: off-by-one poll check when draining an event notifier When an event source is removed (on the death of an application), the notification thread "drains" any remaining notifications from the event notifier pipe. In doing so, it creates a new poll set containing the event source to check if messages are left in the event notification pipe. The invocation of `LTTNG_POLL_GETEV(&events, 1)` means to check the events pending for the first (and only) fd in the poll set. This check is off by one since `0` should be used. For some reason, this worked everywhere except when using a 32-bit userland on a 64-bit kernel (on x86_64). Signed-off-by: Jérémie Galarneau Change-Id: I6f274fdd7c80d5676fd48ae20a14adb3cc010142 --- diff --git a/src/bin/lttng-sessiond/notification-thread-events.c b/src/bin/lttng-sessiond/notification-thread-events.c index 6bd799279..747902612 100644 --- a/src/bin/lttng-sessiond/notification-thread-events.c +++ b/src/bin/lttng-sessiond/notification-thread-events.c @@ -2017,7 +2017,7 @@ int drain_event_notifier_notification_pipe( * the pipe is closed but empty. */ ret = lttng_poll_wait_interruptible(&events, 0); - if (ret == 0 || (LTTNG_POLL_GETEV(&events, 1) & LPOLLIN) == 0) { + if (ret == 0 || (LTTNG_POLL_GETEV(&events, 0) & LPOLLIN) == 0) { /* No more notification to be read on this pipe. */ ret = 0; goto end;