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add pthread_attr_setstack interface (and get)

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i originally omitted these (optional, per POSIX) interfaces because i
considered them backwards implementation details. however, someone
later brought to my attention a fairly legitimate use case: allocating
thread stacks in memory that's setup for sharing and/or fast transfer
between CPU and GPU so that the thread can move data to a GPU directly
from automatic-storage buffers without having to go through additional
buffer copies.

perhaps there are other situations in which these interfaces are
useful too.
This commit is contained in:
Rich Felker 2012-06-09 19:53:29 -04:00
parent f457b1cb0d
commit 819006a88b
4 changed files with 39 additions and 10 deletions
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3
src/internal/pthread_impl.h
View File

@ -59,7 +59,8 @@ struct __timer {
#define _a_stacksize __u.__s[0]
#define _a_guardsize __u.__s[1]
#define _a_detach __u.__i[2*__SU+0]
#define _a_stackaddr __u.__s[2]
#define _a_detach __u.__i[3*__SU+0]
#define _m_type __u.__i[0]
#define _m_lock __u.__i[1]
#define _m_waiters __u.__i[2]

10
src/thread/pthread_attr_getstack.c Normal file
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@ -0,0 +1,10 @@
#include "pthread_impl.h"
int pthread_attr_getstack(const pthread_attr_t *a, void **addr, size_t *size)
{
if (!a->_a_stackaddr)
return EINVAL;
*size = a->_a_stacksize + DEFAULT_STACK_SIZE;
*addr = (void *)(a->_a_stackaddr - *size);
return 0;
}

14
src/thread/pthread_attr_setstack.c Normal file
View File

@ -0,0 +1,14 @@
#include "pthread_impl.h"
/* pthread_key_create.c overrides this */
static const size_t dummy = 0;
weak_alias(dummy, __pthread_tsd_size);
int pthread_attr_setstack(pthread_attr_t *a, void *addr, size_t size)
{
if (size-PTHREAD_STACK_MIN-__pthread_tsd_size > SIZE_MAX/4)
return EINVAL;
a->_a_stackaddr = (size_t)addr + size;
a->_a_stacksize = size - DEFAULT_STACK_SIZE;
return 0;
}

22
src/thread/pthread_create.c
View File

@ -98,16 +98,20 @@ int pthread_create(pthread_t *res, const pthread_attr_t *attr, void *(*entry)(vo
libc.threaded = 1;
}
if (attr) {
guard = ROUND(attr->_a_guardsize + DEFAULT_GUARD_SIZE);
size = guard + ROUND(attr->_a_stacksize + DEFAULT_STACK_SIZE);
if (attr && attr->_a_stackaddr) {
map = 0;
tsd = (void *)(attr->_a_stackaddr-__pthread_tsd_size & -16);
} else {
if (attr) {
guard = ROUND(attr->_a_guardsize + DEFAULT_GUARD_SIZE);
size = guard + ROUND(attr->_a_stacksize + DEFAULT_STACK_SIZE);
}
size += __pthread_tsd_size;
map = mmap(0, size, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0);
if (map == MAP_FAILED) return EAGAIN;
if (guard) mprotect(map, guard, PROT_NONE);
tsd = map + size - __pthread_tsd_size;
}
size += __pthread_tsd_size;
map = mmap(0, size, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0);
if (map == MAP_FAILED) return EAGAIN;
if (guard) mprotect(map, guard, PROT_NONE);
tsd = map + size - __pthread_tsd_size;
new = (void *)(tsd - sizeof *new - PAGE_SIZE%sizeof *new);
new->map_base = map;
new->map_size = size;