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authorRaghavendra G <rgowdapp@redhat.com>2017-08-29 15:07:53 +0530
committerRaghavendra G <rgowdapp@redhat.com>2017-09-06 06:20:42 +0000
commitb1b49997574eeb7c6a42e6e8257c81ac8d2d7578 (patch)
treea4ca6fff26df4f5c2d7d93aa4d617ac6ffd1b21e /cli
parente50fc8f4e7eb51386f47bea9e6ca8d8490c09003 (diff)
event/epoll: don't call handler for events received after a pollerr
we register socket with EPOLLONESHOT, which means it has to be explicitly added back through epoll_ctl to receive more events. Normally we do this once the handler completes processing of current event. But event_select_on_epoll is one asynchronous codepath where socket can be added back for polling while an event on the same socket is being processed. event_select_on_epoll has a check whether an event is being processed in the form of slot->in_handler. But this check is not sufficient enough to prevent parallel events as slot->in_handler is not atomically incremented with respect to reception of the event. This means following imaginary sequence of events can happen: * epoll_wait returns with a POLLERR - say POLLERR1 - on a socket (sock1) associated with slot s1. socket_event_handle_pollerr is yet to be invoked. * an event_select_on called from __socket_ioq_churn which was called in request/reply/msg submission codepath (as opposed to __socket_ioq_churn called as part of POLLOUT handling - we cannot receive a POLLOUT due to EPOLLONESHOT) adds back sock1 for polling. * since sock1 was added back for polling in step 2 and our polling is level-triggered, another thread picks up another POLLERR event - say POLLERR2. socket_event_handler is invoked as part of processing POLLERR2 and it completes execution setting priv->sock to -1. * event_unregister_epoll called as part of __socket_reset due to POLLERR1 would receive fd as -1 resulting in assert failure. Also, since the first pollerr event has done rpc_transport_unref, subsequent parallel events (not just pollerr, but other events too) could be acting on a freed up transport too. Change-Id: I5db755068e7890ec755b59f7a35a57da110339eb BUG: 1486134 Signed-off-by: Raghavendra G <rgowdapp@redhat.com> Reviewed-on: https://review.gluster.org/18129 Smoke: Gluster Build System <jenkins@build.gluster.org> CentOS-regression: Gluster Build System <jenkins@build.gluster.org> Reviewed-by: mohammed rafi kc <rkavunga@redhat.com>
Diffstat (limited to 'cli')
0 files changed, 0 insertions, 0 deletions