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Andrea Parri
c5dcb3aadc
Rearming a queued timer with nonzero slack can leave the timerqueue out of order. remove_and_enqueue_same_base() checks the new soft expiry against its neighbours' hard expiries, then stores the new hard expiry in the node without requeueing it. For example, with A at 10 and B at 20, rearming A at 11 with slack 30 passes the neighbour check but leaves A's hard expiry of 41 before B's 20. The same function also caches the soft expiry in base->expires_next when updating or inserting the first timer, giving next-event selection an earlier deadline than the queue head's hard expiry. Set the timer expiry before handling the queue. Use its stored hard expiry for the in-place ordering check and both updates to base->expires_next. The early update is safe because remove_and_enqueue_same_base() runs with base->cpu_base->lock held. The lock keeps the queue stable while hrtimer_can_update_in_place() checks the new expiry against both neighbours. If the check fails, timerqueue_linked_del() removes the node without comparing expiry values before it is reinserted. Fixes:eddffab828("hrtimer: Keep track of first expiring timer per clock base") Fixes:343f2f4dc5("hrtimer: Try to modify timers in place") Signed-off-by: Andrea Parri <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Assisted-by: LLM Cc: [email protected] Link: https://patch.msgid.link/[email protected]