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authorJeff Dike <jdike@addtoit.com>2006-03-27 09:14:40 (GMT)
committerLinus Torvalds <torvalds@g5.osdl.org>2006-03-27 16:44:38 (GMT)
commit5f4e8fd08f3993bc31a7dd91767fdb4da4fe6278 (patch)
tree8bd66ec07c3051d6f6e09fc53c7f2bde20c3c67d
parent1fbbd6844e6a84e5d166ab475dc298d3b89fa4bf (diff)
downloadlinux-5f4e8fd08f3993bc31a7dd91767fdb4da4fe6278.tar.xz
[PATCH] uml: fix thread startup race
This fixes a race in the starting of write_sigio_thread. Previously, some of the data needed by the thread was initialized after the clone. If the thread ran immediately, it would see the uninitialized data, including an empty pollfds, which would cause it to hang. We move the data initialization to before the clone, and adjust the error paths and cleanup accordingly. Signed-off-by: Jeff Dike <jdike@addtoit.com> Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--arch/um/os-Linux/sigio.c55
1 files changed, 27 insertions, 28 deletions
diff --git a/arch/um/os-Linux/sigio.c b/arch/um/os-Linux/sigio.c
index 7604c40..9ba9429 100644
--- a/arch/um/os-Linux/sigio.c
+++ b/arch/um/os-Linux/sigio.c
@@ -29,8 +29,10 @@ static int write_sigio_pid = -1;
* the descriptors closed after it is killed. So, it can't see them change.
* On the UML side, they are changed under the sigio_lock.
*/
-static int write_sigio_fds[2] = { -1, -1 };
-static int sigio_private[2] = { -1, -1 };
+#define SIGIO_FDS_INIT {-1, -1}
+
+static int write_sigio_fds[2] = SIGIO_FDS_INIT;
+static int sigio_private[2] = SIGIO_FDS_INIT;
struct pollfds {
struct pollfd *poll;
@@ -270,49 +272,46 @@ void write_sigio_workaround(void)
/* Did we race? Don't try to optimize this, please, it's not so likely
* to happen, and no more than once at the boot. */
if(write_sigio_pid != -1)
- goto out_unlock;
-
- write_sigio_pid = run_helper_thread(write_sigio_thread, NULL,
- CLONE_FILES | CLONE_VM, &stack, 0);
+ goto out_free;
- if (write_sigio_pid < 0)
- goto out_clear;
+ current_poll = ((struct pollfds) { .poll = p,
+ .used = 1,
+ .size = 1 });
if (write_sigio_irq(l_write_sigio_fds[0]))
- goto out_kill;
+ goto out_clear_poll;
- /* Success, finally. */
memcpy(write_sigio_fds, l_write_sigio_fds, sizeof(l_write_sigio_fds));
memcpy(sigio_private, l_sigio_private, sizeof(l_sigio_private));
- current_poll = ((struct pollfds) { .poll = p,
- .used = 1,
- .size = 1 });
+ write_sigio_pid = run_helper_thread(write_sigio_thread, NULL,
+ CLONE_FILES | CLONE_VM, &stack, 0);
- sigio_unlock();
- return;
+ if (write_sigio_pid < 0)
+ goto out_clear;
- out_kill:
- l_write_sigio_pid = write_sigio_pid;
- write_sigio_pid = -1;
sigio_unlock();
- /* Going to call waitpid, avoid holding the lock. */
- os_kill_process(l_write_sigio_pid, 1);
- goto out_free;
+ return;
- out_clear:
+out_clear:
write_sigio_pid = -1;
- out_unlock:
- sigio_unlock();
- out_free:
+ write_sigio_fds[0] = -1;
+ write_sigio_fds[1] = -1;
+ sigio_private[0] = -1;
+ sigio_private[1] = -1;
+out_clear_poll:
+ current_poll = ((struct pollfds) { .poll = NULL,
+ .size = 0,
+ .used = 0 });
+out_free:
kfree(p);
- out_close2:
+ sigio_unlock();
+out_close2:
close(l_sigio_private[0]);
close(l_sigio_private[1]);
- out_close1:
+out_close1:
close(l_write_sigio_fds[0]);
close(l_write_sigio_fds[1]);
- return;
}
void sigio_cleanup(void)