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Date:   Thu, 4 Feb 2021 14:06:59 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Dmitry Vyukov <dvyukov@google.com>
Cc:     Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Will Deacon <will@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Matt Morehouse <mascasa@google.com>
Subject: Re: Process-wide watchpoints
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On Thu, Feb 04, 2021 at 01:09:13PM +0100, Peter Zijlstra wrote:

> And I need to dig into that fcntl() crud again, see if that's capable of
> doing a SIGTRAP and if it's possible to target that to the task raising
> it, instead of doing a process wide signal delivery.

Hmm, so it might be possible to extend SETOWN_EX to allow
{F_OWNER_TID,0} to mean any current thread.

And I think SETSIG can be used to set SIGTRAP, although I don't see it
setting the fields you wanted, not entirely sure that's fixable.