On Wed, Feb 3, 2021 at 2:37 PM Peter Zijlstra <[email protected]> wrote: > > On Wed, Feb 03, 2021 at 01:49:56PM +0100, Dmitry Vyukov wrote: > > On Wed, Feb 3, 2021 at 1:29 PM Peter Zijlstra <[email protected]> wrote: > > > > > > On Mon, Feb 01, 2021 at 09:50:20AM +0100, Dmitry Vyukov wrote: > > > > Or, alternatively would it be reasonable for perf to generate SIGTRAP > > > > directly on watchpoint hit (like ptrace does)? That's what I am > > > > ultimately trying to do by attaching a bpf program. > > > > > > Perf should be able to generate signals, The perf_event_open manpage > > > lists two ways of trigering signals. The second way doesn't work for > > > you, due to it not working on inherited counters, but would the first > > > work? > > > > > > That is, set attr::wakeup_events and fcntl(F_SETSIG). > > > > The problem is that this sends a signal to the fd owner rather than > > the thread that hit the breakpoint. At least that's what happened in > > our tests. We would like to send a signal to the thread that hit the > > breakpoint. > > Ah indeed.. all of this was aimed at self-monitoring. > > Letting perf send a signal to the monitored task is intrusive.. let me > think on that.
I was thinking of something very similar to that bpf_send_signal that delays sending to exit from irq: https://elixir.bootlin.com/linux/latest/source/kernel/trace/bpf_trace.c#L1091
