On Tue, 2025-05-27 at 15:37 +0200, Nam Cao wrote: > On Wed, May 14, 2025 at 10:43:14AM +0200, Gabriele Monaco wrote: > > Add a per-cpu monitor as part of the sched model: > > * opid: operations with preemption and irq disabled > > Monitor to ensure wakeup and need_resched occur with irq and > > preemption disabled or in irq handlers. > > This monitor reports some warnings: > > $ perf record -e rv:error_opid --call-graph dwarf -a -- ./stress- > epoll > (stress-epoll program from > https://github.com/rouming/test-tools/blob/master/stress-epoll.c) > Thanks for trying it out, and good to know about this stressor. Unfortunately it's a bit hard to understand from this stack trace, but that's very likely a problem in the model. I have a few ideas where that could be but I believe it's something visible only on a physical machine (haven't tested much on x86 bare metal, only VM). You're running on bare metal right? > $ perf script > stress-epoll 315 [003] 527.674724: rv:error_opid: event > preempt_disable not expected in the state preempt_disabled > ffffffff9fdfb34f da_event_opid+0x10f ([kernel.kallsyms]) > ffffffff9fdfb34f da_event_opid+0x10f ([kernel.kallsyms]) > ffffffff9fdfba0d handle_preempt_disable+0x3d > ([kernel.kallsyms]) > ffffffff9fdd32d0 __traceiter_preempt_disable+0x30 > ([kernel.kallsyms]) > ffffffff9fdd38fe trace_preempt_off+0x4e ([kernel.kallsyms]) > ffffffff9fee6c1c vfs_write+0x12c ([kernel.kallsyms]) > ffffffff9fee7128 ksys_write+0x68 ([kernel.kallsyms]) > ffffffffa0bdbd92 do_syscall_64+0xb2 ([kernel.kallsyms]) > ffffffff9fa00130 entry_SYSCALL_64_after_hwframe+0x77 > ([kernel.kallsyms]) > f833f __GI___libc_write+0x4f (/usr/lib/x86_64- > linux-gnu/libc.so.6) > f833f __GI___libc_write+0x4f (/usr/lib/x86_64- > linux-gnu/libc.so.6) > 1937 thread_work+0x47 (/root/test-tools/stress- > epoll) > 891f4 start_thread+0x304 (/usr/lib/x86_64-linux- > gnu/libc.so.6) > 10989b clone3+0x2b (/usr/lib/x86_64-linux- > gnu/libc.so.6) > > stress-epoll 318 [002] 527.674759: rv:error_opid: event > preempt_disable not expected in the state disabled > ffffffff9fdfb34f da_event_opid+0x10f ([kernel.kallsyms]) > ffffffff9fdfb34f da_event_opid+0x10f ([kernel.kallsyms]) > ffffffff9fdfba0d handle_preempt_disable+0x3d > ([kernel.kallsyms]) > ffffffff9fdd32d0 __traceiter_preempt_disable+0x30 > ([kernel.kallsyms]) > ffffffff9fdd38fe trace_preempt_off+0x4e ([kernel.kallsyms]) > ffffffffa0bec1aa _raw_spin_lock_irq+0x1a ([kernel.kallsyms]) > ffffffff9ff4fe73 eventfd_write+0x63 ([kernel.kallsyms]) > ffffffff9fee6be5 vfs_write+0xf5 ([kernel.kallsyms]) > ffffffff9fee7128 ksys_write+0x68 ([kernel.kallsyms]) > ffffffffa0bdbd92 do_syscall_64+0xb2 ([kernel.kallsyms]) > ffffffff9fa00130 entry_SYSCALL_64_after_hwframe+0x77 > ([kernel.kallsyms]) > f833f __GI___libc_write+0x4f (/usr/lib/x86_64- > linux-gnu/libc.so.6) > f833f __GI___libc_write+0x4f (/usr/lib/x86_64- > linux-gnu/libc.so.6) > 1937 thread_work+0x47 (/root/test-tools/stress- > epoll) > 891f4 start_thread+0x304 (/usr/lib/x86_64-linux- > gnu/libc.so.6) > 10989b clone3+0x2b (/usr/lib/x86_64-linux- > gnu/libc.so.6) > > I'm not sure what I'm looking at here. Do you think these are kernel > bugs, > or the monitor is missing some corner cases? > As said, likely a missing corner case, I believe it has to do with IRQs (which is what makes this monitor more complex than it could be). Thanks for the pointers, I'll try reproduce it this way. Gabriele
