Hi Sebastian, Thank you for the review!
On 01/06/2026 16:58, Sebastian Andrzej Siewior wrote: > On 2026-06-01 13:10:05 [+1000], Matthieu Baerts (NGI0) wrote: >> sk_stop_timer_sync() calls del_timer_sync(), which spin-waits for the > There is no del_timer_sync() Indeed, not sure why I put that one. I wanted to say timer_delete_sync() >> timer callback to complete on non-RT kernels. But on PREEMPT_RT, it can >> sleep. Sleeping inside an RCU read-side critical section might trigger a >> lockdep splat. > > It can not sleep. timer_delete_sync() does not sleep. It can block on > spinlock_t and schedule but this is okay within a RCU read section. Sorry, I got confused by the comment in __timer_delete_sync(). > Do you have a report for this? No, sorry. I was exploring the code in timer.c after a related comment from Sashiko [1]. I noticed the comment in __timer_delete_sync() about being able to sleep on PREEMPT_RT, then saw that timer_delete_sync() was called inside a rcu_read_lock(), and I thought it was wrong. I should have tried to reproduce the warning on PREEMPT_RT, but I switched to the next bug instead :-/ Sorry for the noise, let's drop this patch if it is not needed then. [1] https://github.com/multipath-tcp/mptcp_net-next/issues/623 Cheers, Matt -- Sponsored by the NGI0 Core fund.
