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Chris LuandGitHub
1c130c2d47
* fix(mount): close inodeLocks cleanup race that allowed two flock holders
PosixLockTable.getOrCreateInodeLocks released plt.mu before the caller
acquired il.mu. A concurrent maybeCleanupInode could delete the map
entry in that window; the first caller would then insert its lock into
the orphaned inodeLocks while a later caller created a fresh entry in
the map, so findConflict never observed the orphaned lock and two
owners could simultaneously believe they held the same exclusive flock.
This matches the flaky CI failure seen in
TestPosixFileLocking/ConcurrentLockContention:
Error: Should be empty, but was [worker N: flock overlap detected with 2 holders]
Mark removed inodeLocks as dead under plt.mu+il.mu, and have SetLk /
SetLkw recheck the flag after locking il.mu, refetching the live entry
from the map when orphaned. Also delete the map entry only if it still
points to this il, so a racing recreate is not clobbered.
Adds TestConcurrentFlockChurnPreservesMutualExclusion: 16 goroutines x
500 flock/unflock iterations on one inode. Reliably reports 500+
overlaps per run before the fix; clean across 100 race-enabled runs
after.
* fix(mount): extend dead-flag contract to GetLk and self-heal primitives
Address review feedback on the initial cleanup-race fix:
1. GetLk had the same stale-pointer bug as SetLk. A caller could grab
an inodeLocks pointer, have cleanup orphan it and a replacement il
receive a conflicting lock, then answer F_UNLCK off the empty dead
pointer. Add the same dead recheck + refetch loop.
2. getOrCreateInodeLocks and getInodeLocks now treat a dead map entry
as defective: the former replaces it with a fresh inodeLocks, the
latter drops it and returns nil. Production cannot reach that state
(maybeCleanupInode atomically deletes under plt.mu when it sets
dead), but the hardening guarantees the SetLk / SetLkw / GetLk
retry loops always make progress even if a future refactor reorders
those operations, and it lets the white-box tests set up a stale
dead entry without spinning.
3. Strengthen the regression suite:
- TestSetLkRetriesPastDeadInodeLocks: deterministic white-box test
that installs a dead il in the map and asserts SetLk routes the
new lock into a fresh il (not the orphan), that GetLk reports the
resulting conflict, and that a different-owner acquire is rejected
with EAGAIN.
- TestGetInodeLocksEvictsDeadEntry: verifies both map-read primitives
drop or replace dead entries.
- TestConcurrentFlockChurnPreservesMutualExclusion: replace the
timing-fragile Add(1)-and-check counter with a Swap+CAS detector.
Each worker claims a slot after SetLk OK and releases it before
UN, flagging both an observed predecessor and a lost CAS on
release. Against a reverted fix the detector fires 1000+ times per
run; with the fix clean across 100 race-enabled iterations.
* test(mount): fail fast on unexpected SetLk statuses in churn loop
The stress test blindly spun on any non-OK SetLk status and discarded
the unlock return. If SetLk ever returns something other than OK or
EAGAIN (e.g. after a future refactor introduces a new error), the
acquire loop would spin forever and an unlock failure would be
silently swallowed.
Capture the acquire status, retry only on the expected EAGAIN, and
assert unlock returns OK. Use t.Errorf + return (not t.Fatalf) because
the checks run on worker goroutines where FailNow is unsafe. The
Swap+CAS overlap detector is unchanged.