rqspinlock/tas #10796
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rqspinlock/tas #10796
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The TAS fallback can be invoked directly when queued spin locks are disabled, and through the slow path when paravirt is enabled for queued spin locks. In the latter case, the res_spin_lock macro will attempt the fast path and already hold the entry when entering the slow path. This will lead to creation of extraneous entries that are not released, which may cause false positives for deadlock detection. Fix this by always preceding invocation of the TAS fallback in every case with the grabbing of the held lock entry, and add a comment to make note of this. Fixes: c9102a6 ("rqspinlock: Add a test-and-set fallback") Reported-by: Amery Hung <ameryhung@gmail.com> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
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Pull request overview
This PR refactors the deadlock detection entry management in the resilient spinlock implementation by moving the grab_held_lock_entry call from inside resilient_tas_spin_lock to its call sites.
Changes:
- Removed
grab_held_lock_entrycall fromresilient_tas_spin_lockfunction - Updated
res_spin_lockmacro to callgrab_held_lock_entrybefore invokingresilient_tas_spin_lock - Updated comment to document that deadlock detection entry is grabbed at call sites
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
| kernel/bpf/rqspinlock.c | Removes the grab_held_lock_entry call and updates the comment to explain that the entry is grabbed at call sites |
| include/asm-generic/rqspinlock.h | Updates the res_spin_lock macro to call grab_held_lock_entry before resilient_tas_spin_lock for non-queued spinlocks |
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