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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
commit 819006a88b
4 changed files with 39 additions and 10 deletions
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22
src/thread/pthread_create.c
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@ -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;