From 44a3eaeba04ef78835ca741592c376428ada5f71 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?J=C3=B6rg=20Frings-F=C3=BCrst?= Date: Sat, 2 Dec 2017 10:30:25 +0100 Subject: New upstream version 0.9.8 --- tests/test-rwlock1.c | 157 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 157 insertions(+) create mode 100644 tests/test-rwlock1.c (limited to 'tests/test-rwlock1.c') diff --git a/tests/test-rwlock1.c b/tests/test-rwlock1.c new file mode 100644 index 0000000..e68e59d --- /dev/null +++ b/tests/test-rwlock1.c @@ -0,0 +1,157 @@ +/* Test of glthread_rwlock_rdlock function. + Copyright (C) 2017 Free Software Foundation, Inc. + + This program is free software: you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 3 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see . */ + +/* Written by Bruno Haible , 2005. + Inspired by + https://github.com/linux-test-project/ltp/blob/master/testcases/open_posix_testsuite/conformance/interfaces/pthread_rwlock_rdlock/2-2.c + by Intel Corporation. */ + +#include + +#include "glthread/lock.h" + +#include +#include +#include +#include + +#include "glthread/thread.h" +#include "glthread/yield.h" + +/* Verify that in a situation where + - an rwlock is taken by a reader and has a writer waiting, + - an additional reader requests the lock, + - the waiting writer and the requesting reader threads have the same + priority, + the requesting reader thread gets blocked, so that at some point the + waiting writer can acquire the lock. + Without such a guarantee, when there a N readers and each of the readers + spends more than 1/Nth of the time with the lock held, there is a high + probability that the waiting writer will not get the lock in a given finite + time, a phenomenon called "writer starvation". + Without such a guarantee, applications have a hard time avoiding writer + starvation. + + POSIX:2008 makes this requirement only for implementations that support TPS + (Thread Priority Scheduling) and only for the scheduling policies SCHED_FIFO + and SCHED_RR, see + http://pubs.opengroup.org/onlinepubs/9699919799/functions/pthread_rwlock_rdlock.html + but test verifies the guarantee regardless of TPS and regardless of + scheduling policy. */ + +#define SUCCEED() exit (0) +#define FAILURE() exit (1) +#define UNEXPECTED(n) (fprintf (stderr, "Unexpected outcome %d\n", n), abort ()) + +/* The main thread creates the waiting writer and the requesting reader threads + in the default way; this guarantees that they have the same priority. + We can reuse the main thread as first reader thread. */ + +static gl_rwlock_t lock; +static gl_thread_t reader1; +static gl_thread_t writer; +static gl_thread_t reader2; +static gl_thread_t timer; +/* Used to pass control from writer to reader2 and from reader2 to timer, + as in a relay race. + Passing control from one running thread to another running thread + is most likely faster than to create the second thread. */ +static gl_lock_t baton; + +static void * +timer_func (void *ignored) +{ + /* Step 13 (can be before or after step 12): + The timer thread takes the baton, then waits a moment to make sure + it can tell whether the second reader thread is blocked at step 12. */ + if (glthread_lock_lock (&baton)) + UNEXPECTED (13); + usleep (100000); + /* By the time we get here, it's clear that the second reader thread is + blocked at step 12. This is the desired behaviour. */ + SUCCEED (); +} + +static void * +reader2_func (void *ignored) +{ + int err; + + /* Step 8 (can be before or after step 7): + The second reader thread takes the baton, then waits a moment to make sure + the writer thread has reached step 7. */ + if (glthread_lock_lock (&baton)) + UNEXPECTED (8); + usleep (100000); + /* Step 9 omitted. */ + /* Step 10: Launch a timer, to test whether the next call blocks. */ + if (glthread_create (&timer, timer_func, NULL)) + UNEXPECTED (10); + /* Step 11: Release the baton. */ + if (glthread_lock_unlock (&baton)) + UNEXPECTED (11); + /* Step 12: The second reader thread requests the lock. */ + err = glthread_rwlock_rdlock (&lock); + if (err == 0) + FAILURE (); + else + UNEXPECTED (12); +} + +static void * +writer_func (void *ignored) +{ + /* Step 4: Take the baton, so that the second reader thread does not go ahead + too early. */ + if (glthread_lock_lock (&baton)) + UNEXPECTED (4); + /* Step 5: Create the second reader thread. */ + if (glthread_create (&reader2, reader2_func, NULL)) + UNEXPECTED (5); + /* Step 6: Release the baton. */ + if (glthread_lock_unlock (&baton)) + UNEXPECTED (6); + /* Step 7: The writer thread requests the lock. */ + if (glthread_rwlock_wrlock (&lock)) + UNEXPECTED (7); + return NULL; +} + +int +main () +{ + reader1 = gl_thread_self (); + + /* Step 1: The main thread initializes the lock and the baton. */ + if (glthread_rwlock_init (&lock)) + UNEXPECTED (1); + if (glthread_lock_init (&baton)) + UNEXPECTED (1); + /* Step 2: The main thread acquires the lock as a reader. */ + if (glthread_rwlock_rdlock (&lock)) + UNEXPECTED (2); + /* Step 3: Create the writer thread. */ + if (glthread_create (&writer, writer_func, NULL)) + UNEXPECTED (3); + /* Job done. Go to sleep. */ + for (;;) + { + /* In cooperative threads implementations (Pth), give other threads + a chance to run. */ + gl_thread_yield (); + sleep (1); + } +} -- cgit v1.2.3