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Re: LIBC_PROBE and locks
- From: "Carlos O'Donell" <carlos at redhat dot com>
- To: Florian Weimer <fweimer at redhat dot com>
- Cc: GNU C Library <libc-alpha at sourceware dot org>
- Date: Tue, 17 Nov 2015 10:39:01 -0500
- Subject: Re: LIBC_PROBE and locks
- Authentication-results: sourceware.org; auth=none
- References: <564A1849 dot 1040304 at redhat dot com> <564AAB0E dot 8060806 at redhat dot com> <564B35BC dot 3030300 at redhat dot com>
On 11/17/2015 09:12 AM, Florian Weimer wrote:
> On 11/17/2015 05:20 AM, Carlos O'Donell wrote:
>> On 11/16/2015 12:54 PM, Florian Weimer wrote:
>>> Is it okay to call LIBC_PROBE while internal locks are held? Or could
>>> this result in deadlocks by itself? (I'm aware that the arguments are
>>> always evaluated.)
>>
>> How would it cause deadlocks? The external observer, say systemtap or
>> gdb, are outside of the process and should not modify the state of the
>> process in such a way as to cause a deadlock. Under what conditions might
>> the evaluation of the arguments cause a deadlock?
>
> Are only external observers supported? I wasn't sure if this is some
> sort of self-observing capability which is supposed to work, in which
> case this would be some sort of callback mechanism and subject to
> similar locking issues.
>
> Frank tells me that self-inspection isn't supported, so my concern is
> unfounded.
Agreed. Self-inspection was not considered in the design. It gets
complicated really fast.
Cheers,
Carlos.