From: Alexei Starovoitov Date: Sat, 29 Nov 2025 17:35:36 +0000 (-0800) Subject: Merge branch 'limited-queueing-in-nmi-for-rqspinlock' X-Git-Url: https://gentwo.org/gitweb/?a=commitdiff_plain;h=34235a3544f20291819c20d1d6c4ba07784045a2;p=linux%2F.git Merge branch 'limited-queueing-in-nmi-for-rqspinlock' Kumar Kartikeya Dwivedi says: ==================== Limited queueing in NMI for rqspinlock Ritesh reported that he was frequently seeing timeouts in cases which should have been covered by the AA heuristics. This led to the discovery of multiple gaps in the current code that could lead to timeouts when AA heuristics could work to prevent them. More details and investigation is available in the original threads. [0][1] This set restores the ability for NMI waiters to queue in the slow path, and reduces the cases where they would attempt to trylock. However, such queueing must not happen when interrupting waiters which the NMI itself depends upon for forward progress; in those cases the trylock fallback remains, but with a single attempt to avoid aimless attempts to acquire the lock. It also closes a possible window in the lock fast path and the unlock path where NMIs landing between cmpxchg and entry creation, or entry deletion and unlock would miss the detection of an AA scenario and end up timing out. This virtually eliminates all the cases where existing heuristics can prevent timeouts and quickly recover from a deadlock. More details are available in the commit logs for each patch. [0]: https://lore.kernel.org/bpf/CAH6OuBTjG+N=+GGwcpOUbeDN563oz4iVcU3rbse68egp9wj9_A@mail.gmail.com [1]: https://lore.kernel.org/bpf/20251125203253.3287019-1-memxor@gmail.com ==================== Link: https://patch.msgid.link/20251128232802.1031906-1-memxor@gmail.com Signed-off-by: Alexei Starovoitov --- 34235a3544f20291819c20d1d6c4ba07784045a2