On Fri, 23 Jul 2021 00:43:13 +0200 Stefan Metzmacher <metze@xxxxxxxxx> wrote: > Hi Steve, Hi Stefan, > > After some days of training: > https://training.linuxfoundation.org/training/linux-kernel-debugging-and-security/ > I was able to get much closer to the problem :-) > > In order to reproduce it and get reliable kexec crash dumps, > I needed to give the VM at least 3 cores. > > While running './io-uring_cp-forever link-cp.c file' (from: > https://github.com/metze-samba/liburing/commits/io_uring-cp-forever ) > in one window, the following simple sequence triggered the problem in most cases: > > echo 1 > /sys/kernel/tracing/events/sched/sched_waking/enable > echo 1 > /sys/kernel/tracing/set_event_pid I was able to reproduce it with running hackbench in a while loop and in another terminal, executing the above two lines. I think I found the bug. Can you test this patch? Thanks, -- Steve diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c index 976bf8ce8039..fc32821f8240 100644 --- a/kernel/tracepoint.c +++ b/kernel/tracepoint.c @@ -299,8 +299,8 @@ static int tracepoint_add_func(struct tracepoint *tp, * a pointer to it. This array is referenced by __DO_TRACE from * include/linux/tracepoint.h using rcu_dereference_sched(). */ - rcu_assign_pointer(tp->funcs, tp_funcs); tracepoint_update_call(tp, tp_funcs, false); + rcu_assign_pointer(tp->funcs, tp_funcs); static_key_enable(&tp->key); release_probes(old);
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