add pthread_attr_setstack interface (and get)
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.
diff --git a/src/thread/pthread_create.c b/src/thread/pthread_create.c
index 5b34e7e..48290d3 100644
--- a/src/thread/pthread_create.c
+++ b/src/thread/pthread_create.c
@@ -98,16 +98,20 @@
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;