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Re: [RFC PATCH glibc v2] pthread_setspecific: Provide signal-safety across keys
- From: Szabolcs Nagy <szabolcs dot nagy at arm dot com>
- To: Florian Weimer <fw at deneb dot enyo dot de>, Mathieu Desnoyers <mathieu dot desnoyers at efficios dot com>
- Cc: nd at arm dot com, Carlos O'Donell <carlos at redhat dot com>, Ben Maurer <bmaurer at fb dot com>, libc-alpha at sourceware dot org
- Date: Wed, 18 Oct 2017 12:37:44 +0100
- Subject: Re: [RFC PATCH glibc v2] pthread_setspecific: Provide signal-safety across keys
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On 18/10/17 06:33, Florian Weimer wrote:
> * Mathieu Desnoyers:
>
>> @@ -327,7 +328,7 @@ __nptl_deallocate_tsd (void)
>> {
>> /* The first block is allocated as part of the thread
>> descriptor. */
>> - free (level2);
>> + (void) munmap (level2, PTHREAD_KEY_2NDLEVEL_SIZE * sizeof (*level2));
>> THREAD_SETMEM_NC (self, specific, cnt, NULL);
>
> I think __nptl_deallocate_tsd needs to disable signals as well, even
> when the level2 pointer is NULL, and keep them disabled until the
> thread exits. This is not a localized change; I don't know if it is
> safe.
>
dtors must not run with signals blocked (posix does not
say that dtors may see changed signal mask)
i think it's the user's fault if there is async
pthread_getspecific call while a thread is exiting.
the user can block the signals before thread exit
if that's the intended behaviour.