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Date: Mon, 11 Feb 2013 12:14:17 +0100
From: Szabolcs Nagy <nsz@...t70.net>
To: musl@...ts.openwall.com
Subject: Re: [PATCH v3] move the definition of __pthread_tsd_main to
the only compilation unit that references it
* Jens Gustedt <Jens.Gustedt@...ia.fr> [2013-02-11 11:44:21 +0100]:
> - Avoids a const cast that doesn't seem to be very useful.
> - Remove unused __pthread_tsd_size
>
sorry i was wrong, __pthread_tsd_size is used in pthread_create
(i haven't read all the mails yet)
the logic is that it is 0 when pthread_key_create is not
linked to your code so you avoid all the tsd stack overhead
(which is reasonable: in small tools where size and memory
usage matters most you don't often use thread specific data..
especially now that c11 has tls)
same for pthread_self: you only want non-dummy tsd if
pthread_key_create is used
with your change you break pthread_create (now __pthread_tsd_size
is always 0 there) and pthread_create always pulls in the tsd buf
the weak_alias is there for a reason..
> 0 3 src/thread/pthread_key_create.c
> 2 4 src/thread/pthread_self.c
>
> diff --git a/src/thread/pthread_key_create.c b/src/thread/pthread_key_create.c
> index e51cb02..084cbaa 100644
> --- a/src/thread/pthread_key_create.c
> +++ b/src/thread/pthread_key_create.c
> @@ -1,8 +1,5 @@
> #include "pthread_impl.h"
>
> -const size_t __pthread_tsd_size = sizeof(void *) * PTHREAD_KEYS_MAX;
> -void *__pthread_tsd_main[PTHREAD_KEYS_MAX] = { 0 };
> -
> static void (*keys[PTHREAD_KEYS_MAX])(void *);
>
> static void nodtor(void *dummy)
> diff --git a/src/thread/pthread_self.c b/src/thread/pthread_self.c
> index 23dbaa5..af4998d 100644
> --- a/src/thread/pthread_self.c
> +++ b/src/thread/pthread_self.c
> @@ -2,9 +2,7 @@
>
> static struct pthread *main_thread = &(struct pthread){0};
>
> -/* pthread_key_create.c overrides this */
> -static const void *dummy[1] = { 0 };
> -weak_alias(dummy, __pthread_tsd_main);
> +static void *__pthread_tsd_main[PTHREAD_KEYS_MAX];
>
> static int init_main_thread()
> {
> @@ -12,7 +10,7 @@ static int init_main_thread()
> SIGPT_SET, 0, __SYSCALL_SSLEN);
> if (__set_thread_area(TP_ADJ(main_thread)) < 0) return -1;
> main_thread->canceldisable = libc.canceldisable;
> - main_thread->tsd = (void **)__pthread_tsd_main;
> + main_thread->tsd = __pthread_tsd_main;
> main_thread->errno_ptr = __errno_location();
> main_thread->self = main_thread;
> main_thread->tid = main_thread->pid =
> --
> 1.7.9.5
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