fix: split io_uring_submit_and_wait to prevent SQ ring race (issue #1443)#4
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ShukantPal wants to merge 2 commits intomasterfrom
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fix: split io_uring_submit_and_wait to prevent SQ ring race (issue #1443)#4ShukantPal wants to merge 2 commits intomasterfrom
ShukantPal wants to merge 2 commits intomasterfrom
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…bfuse#1443) io_uring_submit_and_wait() was called without holding ring_lock in fuse_uring_thread(), while reply threads concurrently call io_uring_get_sqe()/io_uring_submit() under ring_lock in fuse_uring_commit_sqe(). Both paths modify the SQ ring, causing corruption in multithreaded operation. Split into io_uring_submit() under ring_lock (serialized with other SQ operations) and io_uring_wait_cqe() without the lock (CQ ring is only written by the kernel and safe to read concurrently). Add a post-CQE-processing submit to flush SQEs prepared during handling (resubmits and synchronous replies skip submission when cqe_processing is set).
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Add source-level validation tests that verify the fix for the io_uring SQ ring race condition in fuse_uring_thread(). The tests check that: - io_uring_submit_and_wait() is not used (broken pattern) - io_uring_submit() is called under ring_lock (serialized with fuse_uring_commit_sqe from reply threads) - io_uring_wait_cqe() is called without holding ring_lock (safe since CQ ring is kernel-written) - io_uring_submit() is called after CQE processing to flush deferred SQEs from reply threads These tests reliably fail without the fix and pass with it, avoiding the non-determinism inherent in runtime race condition testing.
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io_uring_submit_and_wait() was called without holding ring_lock in
fuse_uring_thread(), while reply threads concurrently call
io_uring_get_sqe()/io_uring_submit() under ring_lock in
fuse_uring_commit_sqe(). Both paths modify the SQ ring, causing
corruption in multithreaded operation.
Split into io_uring_submit() under ring_lock (serialized with other
SQ operations) and io_uring_wait_cqe() without the lock (CQ ring is
only written by the kernel and safe to read concurrently). Add a
post-CQE-processing submit to flush SQEs prepared during handling
(resubmits and synchronous replies skip submission when
cqe_processing is set).