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authorUlrich Drepper <drepper@redhat.com>2009-05-15 20:42:36 -0700
committerUlrich Drepper <drepper@redhat.com>2009-05-15 20:42:36 -0700
commit9437b427cec6266abd303983848549a5c4ba0d0a (patch)
tree7d3c7df6abb9a33d4f35a3dc20baa59ff1a53ea1
parentbbc5d74dd0bd1c3dbe7ea8515f081dc7e318272c (diff)
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Fix change to prevent cancel signal in unsafe places.
The bits tested to decide when to delay the return when switching off async cancel mode were wrong. Fix that. Also close a race condition in pthread_cancel where the bit indicating the cancellation is unconditionally set even if the cancel type might have changed.
-rw-r--r--nptl/ChangeLog6
-rw-r--r--nptl/cancellation.c8
-rw-r--r--nptl/libc-cancellation.c8
-rw-r--r--nptl/pthread_cancel.c8
4 files changed, 16 insertions, 14 deletions
diff --git a/nptl/ChangeLog b/nptl/ChangeLog
index 74a2a73..f3bd32f 100644
--- a/nptl/ChangeLog
+++ b/nptl/ChangeLog
@@ -1,5 +1,11 @@
2009-05-15 Ulrich Drepper <drepper@redhat.com>
+ * cancellation.c (__pthread_disable_asynccancel): Correct the bits
+ to test when deciding on the delay.
+ * libc-cancellation.c (__libc_disable_asynccancel): Likewise.
+ * pthread_cancel.c: Close race between deciding on sending a signal
+ and setting the CANCELING_BIT bit.
+
* cancellation.c (__pthread_disable_asynccancel): Don't return if
thread is canceled.
* libc-cancellation.c (__libc_disable_asynccancel): Likewise.
diff --git a/nptl/cancellation.c b/nptl/cancellation.c
index 4d528cf..2a6f83d 100644
--- a/nptl/cancellation.c
+++ b/nptl/cancellation.c
@@ -72,10 +72,6 @@ __pthread_disable_asynccancel (int oldtype)
struct pthread *self = THREAD_SELF;
int newval;
-#ifdef THREAD_ATOMIC_AND
- THREAD_ATOMIC_AND (self, cancelhandling, ~CANCELTYPE_BITMASK);
- newval = THREAD_GETMEM (self, cancelhandling);
-#else
int oldval = THREAD_GETMEM (self, cancelhandling);
while (1)
@@ -93,13 +89,13 @@ __pthread_disable_asynccancel (int oldtype)
/* Prepare the next round. */
oldval = curval;
}
-#endif
/* We cannot return when we are being canceled. Upon return the
thread might be things which would have to be undone. The
following loop should loop until the cancellation signal is
delivered. */
- while (__builtin_expect (newval & CANCELED_BITMASK, 0))
+ while (__builtin_expect ((newval & (CANCELING_BITMASK | CANCELED_BITMASK))
+ == CANCELING_BITMASK, 0))
{
lll_futex_wait (&self->cancelhandling, newval, LLL_PRIVATE);
newval = THREAD_GETMEM (self, cancelhandling);
diff --git a/nptl/libc-cancellation.c b/nptl/libc-cancellation.c
index 35ac82b..cada464 100644
--- a/nptl/libc-cancellation.c
+++ b/nptl/libc-cancellation.c
@@ -88,10 +88,6 @@ __libc_disable_asynccancel (int oldtype)
struct pthread *self = THREAD_SELF;
int newval;
-#ifdef THREAD_ATOMIC_AND
- THREAD_ATOMIC_AND (self, cancelhandling, ~CANCELTYPE_BITMASK);
- newval = THREAD_GETMEM (self, cancelhandling);
-#else
int oldval = THREAD_GETMEM (self, cancelhandling);
while (1)
@@ -109,13 +105,13 @@ __libc_disable_asynccancel (int oldtype)
/* Prepare the next round. */
oldval = curval;
}
-#endif
/* We cannot return when we are being canceled. Upon return the
thread might be things which would have to be undone. The
following loop should loop until the cancellation signal is
delivered. */
- while (__builtin_expect (newval & CANCELED_BITMASK, 0))
+ while (__builtin_expect ((newval & (CANCELING_BITMASK | CANCELED_BITMASK))
+ == CANCELING_BITMASK, 0))
{
lll_futex_wait (&self->cancelhandling, newval, LLL_PRIVATE);
newval = THREAD_GETMEM (self, cancelhandling);
diff --git a/nptl/pthread_cancel.c b/nptl/pthread_cancel.c
index a13af56..55bb0da 100644
--- a/nptl/pthread_cancel.c
+++ b/nptl/pthread_cancel.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 2002, 2003, 2004 Free Software Foundation, Inc.
+/* Copyright (C) 2002, 2003, 2004, 2009 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
@@ -44,6 +44,7 @@ pthread_cancel (th)
int newval;
do
{
+ again:
oldval = pd->cancelhandling;
newval = oldval | CANCELING_BITMASK | CANCELED_BITMASK;
@@ -59,7 +60,10 @@ pthread_cancel (th)
if (CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS (newval))
{
/* Mark the cancellation as "in progress". */
- atomic_bit_set (&pd->cancelhandling, CANCELING_BIT);
+ if (atomic_compare_and_exchange_bool_acq (&pd->cancelhandling,
+ oldval | CANCELING_BITMASK,
+ oldval))
+ goto again;
/* The cancellation handler will take care of marking the
thread as canceled. */