core/mbox: fix race condition [backport 2022.10] #18960
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benpicco
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#18959 is in front of the CI queue, so let's wait for that to be merged |
maribu
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The mbox code contains a race condition in `mbox_put()`: When it waits for a slot in the queue to become available, it is woken up with IRQs enabled. It disables IRQs again as first thing, but by then another thread may already have preempted the running thread and filled the queue back up. In this case, a message in the queue would be silently overwritten. (cherry picked from commit 42b9334)
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It's in, this PR is rebased and back into the CI queue :) |
Murdock results✔️ PASSED 231b1a1 core/mbox: fix race condition
ArtifactsThis only reflects a subset of all builds from https://ci-prod.riot-os.org. Please refer to https://ci.riot-os.org for a complete build for now. |
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Backport of #18955
Contribution description
The mbox code contains a race condition in
mbox_put(): When it waits for a slot in the queue to become available, it is woken up with IRQs enabled. It disables IRQs again as first thing, but by then another thread may already have preempted the running thread and filled the queue back up. In this case, a message in the queue would be silently overwritten.Testing procedure
Actually triggering the race condition would require some effort with a specially crafted test application, which I am unable to currently provide. It should however be quite easy to reason that the change fixes the potential race condition.
In addition, the usual regression tests may make sense.
Issues/PRs references
None