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authorDaniel Jacobowitz <drow@sources.redhat.com>2009-10-30 01:00:44 -0700
committerUlrich Drepper <drepper@redhat.com>2009-10-30 01:00:44 -0700
commit25db0f6ca996f799de308aa2dc7c62caa99ee9dc (patch)
tree96e757452ac19106c74587f208c02e9e10455398 /nptl/allocatestack.c
parent31c759bf37a7a41faf8b13800deb769e8a5f3871 (diff)
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Fix races in setXid implementation.
Diffstat (limited to 'nptl/allocatestack.c')
-rw-r--r--nptl/allocatestack.c123
1 files changed, 104 insertions, 19 deletions
diff --git a/nptl/allocatestack.c b/nptl/allocatestack.c
index 67ea0c6..3c3585f 100644
--- a/nptl/allocatestack.c
+++ b/nptl/allocatestack.c
@@ -965,22 +965,53 @@ __find_thread_by_id (pid_t tid)
static void
internal_function
-setxid_signal_thread (struct xid_command *cmdp, struct pthread *t)
+setxid_mark_thread (struct xid_command *cmdp, struct pthread *t)
{
- if (! IS_DETACHED (t))
+ int ch;
+
+ /* Don't let the thread exit before the setxid handler runs. */
+ t->setxid_futex = 0;
+
+ do
{
- int ch;
- do
- {
- ch = t->cancelhandling;
+ ch = t->cancelhandling;
- /* If the thread is exiting right now, ignore it. */
- if ((ch & EXITING_BITMASK) != 0)
- return;
- }
- while (atomic_compare_and_exchange_bool_acq (&t->cancelhandling,
- ch | SETXID_BITMASK, ch));
+ /* If the thread is exiting right now, ignore it. */
+ if ((ch & EXITING_BITMASK) != 0)
+ return;
}
+ while (atomic_compare_and_exchange_bool_acq (&t->cancelhandling,
+ ch | SETXID_BITMASK, ch));
+}
+
+
+static void
+internal_function
+setxid_unmark_thread (struct xid_command *cmdp, struct pthread *t)
+{
+ int ch;
+
+ do
+ {
+ ch = t->cancelhandling;
+ if ((ch & SETXID_BITMASK) == 0)
+ return;
+ }
+ while (atomic_compare_and_exchange_bool_acq (&t->cancelhandling,
+ ch & ~SETXID_BITMASK, ch));
+
+ /* Release the futex just in case. */
+ t->setxid_futex = 1;
+ lll_futex_wake (&t->setxid_futex, 1, LLL_PRIVATE);
+}
+
+
+static int
+internal_function
+setxid_signal_thread (struct xid_command *cmdp, struct pthread *t)
+{
+ if ((t->cancelhandling & SETXID_BITMASK) == 0)
+ return 0;
int val;
INTERNAL_SYSCALL_DECL (err);
@@ -997,8 +1028,14 @@ setxid_signal_thread (struct xid_command *cmdp, struct pthread *t)
val = INTERNAL_SYSCALL (tkill, err, 2, t->tid, SIGSETXID);
#endif
+ /* If this failed, it must have had not started yet or else exited. */
if (!INTERNAL_SYSCALL_ERROR_P (val, err))
- atomic_increment (&cmdp->cntr);
+ {
+ atomic_increment (&cmdp->cntr);
+ return 1;
+ }
+ else
+ return 0;
}
@@ -1006,6 +1043,7 @@ int
attribute_hidden
__nptl_setxid (struct xid_command *cmdp)
{
+ int signalled;
int result;
lll_lock (stack_cache_lock, LLL_PRIVATE);
@@ -1022,7 +1060,7 @@ __nptl_setxid (struct xid_command *cmdp)
if (t == self)
continue;
- setxid_signal_thread (cmdp, t);
+ setxid_mark_thread (cmdp, t);
}
/* Now the list with threads using user-allocated stacks. */
@@ -1032,14 +1070,61 @@ __nptl_setxid (struct xid_command *cmdp)
if (t == self)
continue;
- setxid_signal_thread (cmdp, t);
+ setxid_mark_thread (cmdp, t);
}
- int cur = cmdp->cntr;
- while (cur != 0)
+ /* Iterate until we don't succeed in signalling anyone. That means
+ we have gotten all running threads, and their children will be
+ automatically correct once started. */
+ do
{
- lll_futex_wait (&cmdp->cntr, cur, LLL_PRIVATE);
- cur = cmdp->cntr;
+ signalled = 0;
+
+ list_for_each (runp, &stack_used)
+ {
+ struct pthread *t = list_entry (runp, struct pthread, list);
+ if (t == self)
+ continue;
+
+ signalled += setxid_signal_thread (cmdp, t);
+ }
+
+ list_for_each (runp, &__stack_user)
+ {
+ struct pthread *t = list_entry (runp, struct pthread, list);
+ if (t == self)
+ continue;
+
+ signalled += setxid_signal_thread (cmdp, t);
+ }
+
+ int cur = cmdp->cntr;
+ while (cur != 0)
+ {
+ lll_futex_wait (&cmdp->cntr, cur, LLL_PRIVATE);
+ cur = cmdp->cntr;
+ }
+ }
+ while (signalled != 0);
+
+ /* Clean up flags, so that no thread blocks during exit waiting
+ for a signal which will never come. */
+ list_for_each (runp, &stack_used)
+ {
+ struct pthread *t = list_entry (runp, struct pthread, list);
+ if (t == self)
+ continue;
+
+ setxid_unmark_thread (cmdp, t);
+ }
+
+ list_for_each (runp, &__stack_user)
+ {
+ struct pthread *t = list_entry (runp, struct pthread, list);
+ if (t == self)
+ continue;
+
+ setxid_unmark_thread (cmdp, t);
}
/* This must be last, otherwise the current thread might not have