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From: Florian Weimer <fweimer@redhat.com>
To: Szabolcs Nagy <szabolcs.nagy@arm.com>
Cc: Carlos O'Donell <codonell@redhat.com>,
	 nd@arm.com,  GNU C Library <libc-alpha@sourceware.org>
Subject: Re: [PATCH] Reserve static TLS for dynamically loaded initial-exec TLS only [BZ #25051]
Date: Thu, 27 Feb 2020 17:31:02 +0100	[thread overview]
Message-ID: <87lfoovvp5.fsf@oldenburg2.str.redhat.com> (raw)
In-Reply-To: <d2d07b0f-7be4-630c-a2ac-2f3f680b79ae@arm.com> (Szabolcs Nagy's message of "Thu, 27 Feb 2020 16:21:17 +0000")

* Szabolcs Nagy:

> it has correctness implications too, e.g. in case of
> errno or soft-float fenv emulation (ppc only?) tls
> access may happen in signal handlers and i think
> currently only initial (and local) exec tls is
> guaranteed to be as-safe.

I think you are probably right.  (I don't have the performance numbers
yet.)

> libc also has struct pthread, i wonder if any of that
> needs to be duplicated for dlmopen (is it valid to
> dlmopen a different version of libc.so.6 ?)

Not a different version, but you get a different copy, including a fresh
set of TLS variables (hence the dlmopen limitation).  But obviously not
of struct pthread and the TCB.  Now that Hurd supports THREAD_GETMEM, we
can make a choice whether we want to share per-thread data across the
dlmopen boundary or not.

Thanks,
Florian


      reply	other threads:[~2020-02-27 16:31 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-07 11:54 [PATCH] Reserve static TLS for dynamically loaded initial-exec TLS only [BZ #25051] Szabolcs Nagy
2020-01-07 12:09 ` Florian Weimer
2020-01-07 12:50   ` Szabolcs Nagy
2020-02-13 16:38     ` Szabolcs Nagy
2020-02-13 18:07       ` Carlos O'Donell
2020-02-17 16:01         ` Florian Weimer
2020-02-20 15:05           ` Carlos O'Donell
2020-02-21 12:58             ` Florian Weimer
2020-02-27 16:21               ` Szabolcs Nagy
2020-02-27 16:31                 ` Florian Weimer [this message]

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