| 1 | /* Test rwlock with PREFER_WRITER_NONRECURSIVE_NP (bug 23861). |
|---|---|
| 2 | Copyright (C) 2018-2022 Free Software Foundation, Inc. |
| 3 | This file is part of the GNU C Library. |
| 4 | |
| 5 | The GNU C Library is free software; you can redistribute it and/or |
| 6 | modify it under the terms of the GNU Lesser General Public |
| 7 | License as published by the Free Software Foundation; either |
| 8 | version 2.1 of the License, or (at your option) any later version. |
| 9 | |
| 10 | The GNU C Library is distributed in the hope that it will be useful, |
| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 13 | Lesser General Public License for more details. |
| 14 | |
| 15 | You should have received a copy of the GNU Lesser General Public |
| 16 | License along with the GNU C Library; if not, see |
| 17 | <https://www.gnu.org/licenses/>. */ |
| 18 | |
| 19 | #include <stdio.h> |
| 20 | #include <stdlib.h> |
| 21 | #include <unistd.h> |
| 22 | #include <pthread.h> |
| 23 | #include <support/xthread.h> |
| 24 | |
| 25 | /* We choose 10 iterations because this happens to be able to trigger the |
| 26 | stall on contemporary hardware. */ |
| 27 | #define LOOPS 10 |
| 28 | /* We need 3 threads to trigger bug 23861. One thread as a writer, and |
| 29 | two reader threads. The test verifies that the second-to-last reader |
| 30 | is able to notify the *last* reader that it should be done waiting. |
| 31 | If the second-to-last reader fails to notify the last reader or does |
| 32 | so incorrectly then the last reader may stall indefinitely. */ |
| 33 | #define NTHREADS 3 |
| 34 | |
| 35 | _Atomic int do_exit; |
| 36 | pthread_rwlockattr_t mylock_attr; |
| 37 | pthread_rwlock_t mylock; |
| 38 | |
| 39 | void * |
| 40 | run_loop (void *a) |
| 41 | { |
| 42 | while (!do_exit) |
| 43 | { |
| 44 | if (random () & 1) |
| 45 | { |
| 46 | xpthread_rwlock_wrlock (rwlock: &mylock); |
| 47 | xpthread_rwlock_unlock (rwlock: &mylock); |
| 48 | } |
| 49 | else |
| 50 | { |
| 51 | xpthread_rwlock_rdlock (rwlock: &mylock); |
| 52 | xpthread_rwlock_unlock (rwlock: &mylock); |
| 53 | } |
| 54 | } |
| 55 | return NULL; |
| 56 | } |
| 57 | |
| 58 | int |
| 59 | do_test (void) |
| 60 | { |
| 61 | xpthread_rwlockattr_init (attr: &mylock_attr); |
| 62 | xpthread_rwlockattr_setkind_np (attr: &mylock_attr, |
| 63 | pref: PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP); |
| 64 | xpthread_rwlock_init (rwlock: &mylock, attr: &mylock_attr); |
| 65 | |
| 66 | for (int n = 0; n < LOOPS; n++) |
| 67 | { |
| 68 | pthread_t tids[NTHREADS]; |
| 69 | do_exit = 0; |
| 70 | for (int i = 0; i < NTHREADS; i++) |
| 71 | tids[i] = xpthread_create (NULL, thread_func: run_loop, NULL); |
| 72 | /* Let the threads run for some time. */ |
| 73 | sleep (seconds: 1); |
| 74 | printf (format: "Exiting..."); |
| 75 | fflush (stdout); |
| 76 | do_exit = 1; |
| 77 | for (int i = 0; i < NTHREADS; i++) |
| 78 | xpthread_join (thr: tids[i]); |
| 79 | printf (format: "done.\n"); |
| 80 | } |
| 81 | pthread_rwlock_destroy (rwlock: &mylock); |
| 82 | pthread_rwlockattr_destroy (attr: &mylock_attr); |
| 83 | return 0; |
| 84 | } |
| 85 | |
| 86 | #define TIMEOUT (DEFAULT_TIMEOUT + 3 * LOOPS) |
| 87 | #include <support/test-driver.c> |
| 88 |