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6c29942cbf
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.
104 lines
3.3 KiB
C
104 lines
3.3 KiB
C
/* Check if clone (CLONE_THREAD) does not call exit_group (BZ #21512)
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Copyright (C) 2017-2019 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <string.h>
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#include <sched.h>
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#include <signal.h>
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#include <unistd.h>
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#include <sys/syscall.h>
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#include <sys/wait.h>
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#include <sys/types.h>
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#include <linux/futex.h>
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#include <stackinfo.h> /* For _STACK_GROWS_{UP,DOWN}. */
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#include <support/check.h>
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#include <stdatomic.h>
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/* Test if clone call with CLONE_THREAD does not call exit_group. The 'f'
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function returns '1', which will be used by clone thread to call the
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'exit' syscall directly. If _exit is used instead, exit_group will be
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used and thus the thread group will finish with return value of '1'
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(where '2' from main thread is expected. */
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static int
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f (void *a)
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{
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return 1;
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}
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/* Futex wait for TID argument, similar to pthread_join internal
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implementation. */
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#define wait_tid(ctid_ptr, ctid_val) \
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do { \
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__typeof (*(ctid_ptr)) __tid; \
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/* We need acquire MO here so that we synchronize with the \
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kernel's store to 0 when the clone terminates. */ \
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while ((__tid = atomic_load_explicit (ctid_ptr, \
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memory_order_acquire)) != 0) \
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futex_wait (ctid_ptr, ctid_val); \
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} while (0)
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static inline int
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futex_wait (int *futexp, int val)
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{
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return syscall (__NR_futex, futexp, FUTEX_WAIT, val);
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}
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static int
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do_test (void)
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{
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char st[1024] __attribute__ ((aligned));
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int clone_flags = CLONE_THREAD;
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/* Minimum required flags to used along with CLONE_THREAD. */
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clone_flags |= CLONE_VM | CLONE_SIGHAND;
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/* We will used ctid to call on futex to wait for thread exit. */
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clone_flags |= CLONE_CHILD_CLEARTID;
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/* Initialize with a known value. ctid is set to zero by the kernel after the
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cloned thread has exited. */
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#define CTID_INIT_VAL 1
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pid_t ctid = CTID_INIT_VAL;
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pid_t tid;
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#ifdef __ia64__
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extern int __clone2 (int (*__fn) (void *__arg), void *__child_stack_base,
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size_t __child_stack_size, int __flags,
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void *__arg, ...);
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tid = __clone2 (f, st, sizeof (st), clone_flags, NULL, /* ptid */ NULL,
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/* tls */ NULL, &ctid);
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#else
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#if _STACK_GROWS_DOWN
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tid = clone (f, st + sizeof (st), clone_flags, NULL, /* ptid */ NULL,
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/* tls */ NULL, &ctid);
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#elif _STACK_GROWS_UP
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tid = clone (f, st, clone_flags, NULL, /* ptid */ NULL, /* tls */ NULL,
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&ctid);
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#else
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#error "Define either _STACK_GROWS_DOWN or _STACK_GROWS_UP"
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#endif
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#endif
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if (tid == -1)
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FAIL_EXIT1 ("clone failed: %m");
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wait_tid (&ctid, CTID_INIT_VAL);
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return 2;
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}
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#define EXPECTED_STATUS 2
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#include <support/test-driver.c>
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