Re: [PATCH 1/8] perf: Allow to block process in syscall tracepoints

From: Steven Rostedt
Date: Wed Dec 12 2018 - 20:26:45 EST

On Thu, 13 Dec 2018 03:39:38 +0300
"Dmitry V. Levin" <ldv@xxxxxxxxxxxx> wrote:

> btw, I didn't ask for the implementation to be ugly.
> You don't have to introduce polling into the kernel if you don't want to,
> userspace is perfectly capable of invoking wait4(2) in a loop.
> Just block the tracee, notify the tracer, and let it pick up the pieces.

Note, there's been some discussion offlist to only have perf set a flag
when it dropped an event and have the ptrace code do the heavy lifting
of blocking the task and waking it back up. I think that would be a
cleaner solution and wont muck with perf as badly.

-- Steve