From 60164570111873175111cf8a5b973375e492eee9 Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Tue, 27 Sep 2011 13:50:29 -0400 Subject: process-shared barrier support, based on discussion with bdonlan this implementation is rather heavy-weight, but it's the first solution i've found that's actually correct. all waiters actually wait twice at the barrier so that they can synchronize exit, and they hold a "vm lock" that prevents changes to virtual memory mappings (and blocks pthread_barrier_destroy) until all waiters are finished inspecting the barrier. thus, it is safe for any thread to destroy and/or unmap the barrier's memory as soon as pthread_barrier_wait returns, without further synchronization. --- src/mman/mmap.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) (limited to 'src/mman/mmap.c') diff --git a/src/mman/mmap.c b/src/mman/mmap.c index 883acb28..fd2bb07e 100644 --- a/src/mman/mmap.c +++ b/src/mman/mmap.c @@ -5,16 +5,25 @@ #include "syscall.h" #include "libc.h" +static void dummy1(int x) { } +static void dummy0(void) { } +weak_alias(dummy1, __vm_lock); +weak_alias(dummy0, __vm_unlock); + void *__mmap(void *start, size_t len, int prot, int flags, int fd, off_t off) { + void *ret; if (sizeof(off_t) > sizeof(long)) if (((long)off & 0xfff) | ((long)((unsigned long long)off>>(12 + 8*(sizeof(off_t)-sizeof(long)))))) start = (void *)-1; + if (flags & MAP_FIXED) __vm_lock(-1); #ifdef SYS_mmap2 - return (void *)syscall(SYS_mmap2, start, len, prot, flags, fd, off>>12); + ret = (void *)syscall(SYS_mmap2, start, len, prot, flags, fd, off>>12); #else - return (void *)syscall(SYS_mmap, start, len, prot, flags, fd, off); + ret = (void *)syscall(SYS_mmap, start, len, prot, flags, fd, off); #endif + if (flags & MAP_FIXED) __vm_unlock(); + return ret; } weak_alias(__mmap, mmap); -- cgit v1.2.1