bpf: Fix conditions when timer/wq can be called #10949
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added 4 commits
February 3, 2026 22:03
Though hrtimer_start/cancel() inlines all of the smaller helpers in hrtimer.c and only call timerqueue_add/del() from lib/timerqueue.c where everything is not traceable and not kprobe-able (because all files in lib/ are not traceable), there are tracepoints within hrtimer that are called with locks held. Therefore prevent the deadlock by tightening conditions when timer/wq can be called synchronously. hrtimer/wq are using raw_spin_lock_irqsave(), so irqs_disabled() is enough. Fixes: 1bfbc26 ("bpf: Enable bpf_timer and bpf_wq in any context") Signed-off-by: Alexei Starovoitov <[email protected]>
Add a testcase that checks that deadlock avoidance is working as expected. Signed-off-by: Alexei Starovoitov <[email protected]>
Do not schedule timer/wq operation on a cpu that is in irq_work callback that is processing async_cmds queue. Otherwise the following loop is possible: bpf_timer_start() -> bpf_async_schedule_op() -> irq_work_queue(). irqrestore -> bpf_async_irq_worker() -> tracepoint -> bpf_timer_start(). Fixes: 1bfbc26 ("bpf: Enable bpf_timer and bpf_wq in any context") Signed-off-by: Alexei Starovoitov <[email protected]>
Strengthen timer_start_deadlock test and check for recursion now Signed-off-by: Alexei Starovoitov <[email protected]>
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Upstream branch: b28dac3 |
kernel-patches-daemon-bpf
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Pull request for series with
subject: bpf: Tighten conditions when timer/wq can be called synchronously
version: 3
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=1050594