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Re: [RFC PATCH v4 1/5] glibc: Perform rseq(2) registration at nptl init and thread creation
- From: Florian Weimer <fweimer at redhat dot com>
- To: Mathieu Desnoyers <mathieu dot desnoyers at efficios dot com>
- Cc: Rich Felker <dalias at libc dot org>, carlos <carlos at redhat dot com>, Joseph Myers <joseph at codesourcery dot com>, Szabolcs Nagy <szabolcs dot nagy at arm dot com>, libc-alpha <libc-alpha at sourceware dot org>, Thomas Gleixner <tglx at linutronix dot de>, Ben Maurer <bmaurer at fb dot com>, Peter Zijlstra <peterz at infradead dot org>, "Paul E. McKenney" <paulmck at linux dot vnet dot ibm dot com>, Boqun Feng <boqun dot feng at gmail dot com>, Will Deacon <will dot deacon at arm dot com>, Dave Watson <davejwatson at fb dot com>, Paul Turner <pjt at google dot com>, linux-kernel <linux-kernel at vger dot kernel dot org>, linux-api <linux-api at vger dot kernel dot org>
- Date: Thu, 22 Nov 2018 16:11:45 +0100
- Subject: Re: [RFC PATCH v4 1/5] glibc: Perform rseq(2) registration at nptl init and thread creation
- References: <20181121183936.8176-1-mathieu.desnoyers@efficios.com> <20181122143603.GD23599@brightrain.aerifal.cx> <782067422.9852.1542899056778.JavaMail.zimbra@efficios.com>
* Mathieu Desnoyers:
> Thoughts ?
>
> /* Unregister rseq TLS from kernel. */
> if (has_rseq && __rseq_unregister_current_thread ())
> abort();
>
> advise_stack_range (pd->stackblock, pd->stackblock_size, (uintptr_t) pd,
> pd->guardsize);
>
> /* If the thread is detached free the TCB. */
> if (IS_DETACHED (pd))
> /* Free the TCB. */
> __free_tcb (pd);
Considering that we proceed to free the TCB, I really hope that all
signals are blocked at this point. (I have not checked this, though.)
Wouldn't this address your concern about access to the rseq area?
Thanks,
Florian