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authorStefan Liebler <stli@linux.ibm.com>2019-02-18 16:12:01 +0100
committerStefan Liebler <stli@linux.ibm.com>2019-02-18 16:12:01 +0100
commit6c29942cbf059aca47fd4bbd852ea42c9d46b71f (patch)
tree0f51ed545083ac82cb9ed7d115d2c2c6a48d6891
parentad18dadec945329f95b53b63ed69f91878a329df (diff)
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misc/tst-clone3: Fix waiting for exited thread.
From time to time the test misc/tst-clone3 fails with a timeout. Then futex_wait is blocking. Usually ctid should be set to zero due to CLONE_CHILD_CLEARTID and the futex should be waken up. But the fail occures if the thread has already exited before ctid is set to the return value of clone(). Then futex_wait() will block as there will be nobody who wakes the futex up again. This patch initializes ctid to a known value before calling clone and the kernel is the only one who updates the value to zero after clone. If futex_wait is called then it is either waked up due to the exited thread or the futex syscall fails as *ctid_ptr is already zero instead of the specified value 1. ChangeLog: * sysdeps/unix/sysv/linux/tst-clone3.c (do_test): Initialize ctid with a known value and remove update of ctid after clone. (wait_tid): Adjust arguments and call futex_wait with ctid_val as assumed current value of ctid_ptr.
-rw-r--r--ChangeLog8
-rw-r--r--sysdeps/unix/sysv/linux/tst-clone3.c23
2 files changed, 23 insertions, 8 deletions
diff --git a/ChangeLog b/ChangeLog
index 25985141e2..269c7569c9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2019-02-18 Stefan Liebler <stli@linux.ibm.com>
+
+ * sysdeps/unix/sysv/linux/tst-clone3.c (do_test):
+ Initialize ctid with a known value and remove update of ctid
+ after clone.
+ (wait_tid): Adjust arguments and call futex_wait with ctid_val
+ as assumed current value of ctid_ptr.
+
2019-02-15 Florian Weimer <fweimer@redhat.com>
Check that non-sysdeps headers have wrapper headers.
diff --git a/sysdeps/unix/sysv/linux/tst-clone3.c b/sysdeps/unix/sysv/linux/tst-clone3.c
index aa8e718afe..e78755fcd3 100644
--- a/sysdeps/unix/sysv/linux/tst-clone3.c
+++ b/sysdeps/unix/sysv/linux/tst-clone3.c
@@ -27,6 +27,7 @@
#include <stackinfo.h> /* For _STACK_GROWS_{UP,DOWN}. */
#include <support/check.h>
+#include <stdatomic.h>
/* Test if clone call with CLONE_THREAD does not call exit_group. The 'f'
function returns '1', which will be used by clone thread to call the
@@ -42,11 +43,14 @@ f (void *a)
/* Futex wait for TID argument, similar to pthread_join internal
implementation. */
-#define wait_tid(tid) \
- do { \
- __typeof (tid) __tid; \
- while ((__tid = (tid)) != 0) \
- futex_wait (&(tid), __tid); \
+#define wait_tid(ctid_ptr, ctid_val) \
+ do { \
+ __typeof (*(ctid_ptr)) __tid; \
+ /* We need acquire MO here so that we synchronize with the \
+ kernel's store to 0 when the clone terminates. */ \
+ while ((__tid = atomic_load_explicit (ctid_ptr, \
+ memory_order_acquire)) != 0) \
+ futex_wait (ctid_ptr, ctid_val); \
} while (0)
static inline int
@@ -64,7 +68,11 @@ do_test (void)
clone_flags |= CLONE_VM | CLONE_SIGHAND;
/* We will used ctid to call on futex to wait for thread exit. */
clone_flags |= CLONE_CHILD_CLEARTID;
- pid_t ctid, tid;
+ /* Initialize with a known value. ctid is set to zero by the kernel after the
+ cloned thread has exited. */
+#define CTID_INIT_VAL 1
+ pid_t ctid = CTID_INIT_VAL;
+ pid_t tid;
#ifdef __ia64__
extern int __clone2 (int (*__fn) (void *__arg), void *__child_stack_base,
@@ -86,8 +94,7 @@ do_test (void)
if (tid == -1)
FAIL_EXIT1 ("clone failed: %m");
- ctid = tid;
- wait_tid (ctid);
+ wait_tid (&ctid, CTID_INIT_VAL);
return 2;
}