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authorAlexander Kabaev <kan@freebsd.org>2019-11-01 18:26:20 -0400
committerAlexander Kabaev <kan@freebsd.org>2019-11-01 21:57:49 -0400
commitfeda545105106d673fdca61028331c86eeb1f408 (patch)
tree74cb9790744d3f73ac6145910543196bf7ee5c9c /.gitreview
parent5bec5f7860dafcef6aefd50b74de15d08910c6f4 (diff)
vlib: Handle race in thread barrier processing
When CLIB_DEBUG is enabled, vlib_foreach_main macro asserts that vlib_main it currently looks at is safely parked in barrier, by checkling that vlib_main->parked_at_barrier is not 0. Unfortunately, the check is racy - workers first increment the atomic counter to indicate that they have reached the barrier and _then_ set this_main->parked_at_barrier to 1. For the last worker to suspend this opens the race - main thread is free to execute and assert immediately after atomic counter has been incremented, before worker gets to write to own parked_at_barrier. Fix this by simply swapping the order of two operations. Type: fix Signed-off-by: Alexnader Kabaev <kan@FreeBSD.org> Change-Id: Iae47abd6ca0be1c5413f5ecaefabc64cd7eac2ed
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