On 2021-12-15 16:44:12 [+0100], Florent Carli wrote: > Hello all, Hi, … I tried to reproduce this but nothing. However… > If we try the experiment once again, the tap will fail but we won't > get a new backtrace. The backtrace is meant to appear only once. > A first analyzis was done on the #linux-rt irc channel: > "huh, looks like the underlying issue is hitting the WARN_ON_ONCE() > condition in eventfd_signal(), but in the bug handler (which > apparently is preemptible), we get into print_stop_info() and try to > use smp_processor_id() in that context, which is wrong because thigns > are preemptible. > I can't see the smp_processor_id() usage in mainlin (I don't have an > RT tree to hand), but someone with more RT knowledge might want to > look at that" So that smp_processor_id() thingy is sad because the code changed before it hit upstream and I didn't notice it. Patch #1 contains the missing bits and avoids the backtrace from WARN_ON_ONCE(). Patch #2 is a backport from upstream avoiding trigger WARN_ON_ONCE in the first place. Could you please try these two if they help? > Thanks. Sebastian
