futex_requeue_pi_signal_restart.c

  1// SPDX-License-Identifier: GPL-2.0-or-later
  2/******************************************************************************
  3 *
  4 *   Copyright © International Business Machines  Corp., 2006-2008
  5 *
  6 * DESCRIPTION
  7 *      This test exercises the futex_wait_requeue_pi() signal handling both
  8 *      before and after the requeue. The first should be restarted by the
  9 *      kernel. The latter should return EWOULDBLOCK to the waiter.
 10 *
 11 * AUTHORS
 12 *      Darren Hart <dvhart@linux.intel.com>
 13 *
 14 * HISTORY
 15 *      2008-May-5: Initial version by Darren Hart <dvhart@linux.intel.com>
 16 *
 17 *****************************************************************************/
 18
 19#include <errno.h>
 20#include <getopt.h>
 21#include <limits.h>
 22#include <pthread.h>
 23#include <signal.h>
 24#include <stdio.h>
 25#include <stdlib.h>
 26#include <string.h>
 27
 28#include "atomic.h"
 29#include "futextest.h"
 30#include "kselftest_harness.h"
 31
 32#define DELAY_US 100
 33
 34futex_t f1 = FUTEX_INITIALIZER;
 35futex_t f2 = FUTEX_INITIALIZER;
 36atomic_t requeued = ATOMIC_INITIALIZER;
 37
 38int waiter_ret = 0;
 39
 40int create_rt_thread(pthread_t *pth, void*(*func)(void *), void *arg,
 41		     int policy, int prio)
 42{
 43	struct sched_param schedp;
 44	pthread_attr_t attr;
 45	int ret;
 46
 47	pthread_attr_init(&attr);
 48	memset(&schedp, 0, sizeof(schedp));
 49
 50	ret = pthread_attr_setinheritsched(&attr, PTHREAD_EXPLICIT_SCHED);
 51	if (ret)
 52		ksft_exit_fail_msg("pthread_attr_setinheritsched\n");
 53
 54	ret = pthread_attr_setschedpolicy(&attr, policy);
 55	if (ret)
 56		ksft_exit_fail_msg("pthread_attr_setschedpolicy\n");
 57
 58	schedp.sched_priority = prio;
 59	ret = pthread_attr_setschedparam(&attr, &schedp);
 60	if (ret)
 61		ksft_exit_fail_msg("pthread_attr_setschedparam\n");
 62
 63	ret = pthread_create(pth, &attr, func, arg);
 64	if (ret)
 65		ksft_exit_fail_msg("pthread_create\n");
 66
 67	return 0;
 68}
 69
 70void handle_signal(int signo)
 71{
 72	ksft_print_dbg_msg("signal received %s requeue\n",
 73	     requeued.val ? "after" : "prior to");
 74}
 75
 76void *waiterfn(void *arg)
 77{
 78	unsigned int old_val;
 79	int res;
 80
 81	ksft_print_dbg_msg("Waiter running\n");
 82	ksft_print_dbg_msg("Calling FUTEX_LOCK_PI on f2=%x @ %p\n", f2, &f2);
 83	old_val = f1;
 84	res = futex_wait_requeue_pi(&f1, old_val, &(f2), NULL,
 85				    FUTEX_PRIVATE_FLAG);
 86	if (!requeued.val || errno != EWOULDBLOCK) {
 87		ksft_test_result_fail("unexpected return from futex_wait_requeue_pi: %d (%s)\n",
 88		     res, strerror(errno));
 89		ksft_print_dbg_msg("w2:futex: %x\n", f2);
 90		if (!res)
 91			futex_unlock_pi(&f2, FUTEX_PRIVATE_FLAG);
 92	}
 93
 94	pthread_exit(NULL);
 95}
 96
 97
 98TEST(futex_requeue_pi_signal_restart)
 99{
100	unsigned int old_val;
101	struct sigaction sa;
102	pthread_t waiter;
103	int res;
104
105	sa.sa_handler = handle_signal;
106	sigemptyset(&sa.sa_mask);
107	sa.sa_flags = 0;
108	if (sigaction(SIGUSR1, &sa, NULL))
109		ksft_exit_fail_msg("sigaction\n");
110
111	ksft_print_dbg_msg("m1:f2: %x\n", f2);
112	ksft_print_dbg_msg("Creating waiter\n");
113	res = create_rt_thread(&waiter, waiterfn, NULL, SCHED_FIFO, 1);
114	if (res)
115		ksft_exit_fail_msg("Creating waiting thread failed");
116
117	ksft_print_dbg_msg("Calling FUTEX_LOCK_PI on f2=%x @ %p\n", f2, &f2);
118	ksft_print_dbg_msg("m2:f2: %x\n", f2);
119	futex_lock_pi(&f2, 0, 0, FUTEX_PRIVATE_FLAG);
120	ksft_print_dbg_msg("m3:f2: %x\n", f2);
121
122	while (1) {
123		/*
124		 * signal the waiter before requeue, waiter should automatically
125		 * restart futex_wait_requeue_pi() in the kernel. Wait for the
126		 * waiter to block on f1 again.
127		 */
128		ksft_print_dbg_msg("Issuing SIGUSR1 to waiter\n");
129		pthread_kill(waiter, SIGUSR1);
130		usleep(DELAY_US);
131
132		ksft_print_dbg_msg("Requeueing waiter via FUTEX_CMP_REQUEUE_PI\n");
133		old_val = f1;
134		res = futex_cmp_requeue_pi(&f1, old_val, &(f2), 1, 0,
135					   FUTEX_PRIVATE_FLAG);
136		/*
137		 * If res is non-zero, we either requeued the waiter or hit an
138		 * error, break out and handle it. If it is zero, then the
139		 * signal may have hit before the waiter was blocked on f1.
140		 * Try again.
141		 */
142		if (res > 0) {
143			atomic_set(&requeued, 1);
144			break;
145		} else if (res < 0) {
146			ksft_exit_fail_msg("FUTEX_CMP_REQUEUE_PI failed\n");
147		}
148	}
149	ksft_print_dbg_msg("m4:f2: %x\n", f2);
150
151	/*
152	 * Signal the waiter after requeue, waiter should return from
153	 * futex_wait_requeue_pi() with EWOULDBLOCK. Join the thread here so the
154	 * futex_unlock_pi() can't happen before the signal wakeup is detected
155	 * in the kernel.
156	 */
157	ksft_print_dbg_msg("Issuing SIGUSR1 to waiter\n");
158	pthread_kill(waiter, SIGUSR1);
159	ksft_print_dbg_msg("Waiting for waiter to return\n");
160	pthread_join(waiter, NULL);
161
162	ksft_print_dbg_msg("Calling FUTEX_UNLOCK_PI on mutex=%x @ %p\n", f2, &f2);
163	futex_unlock_pi(&f2, FUTEX_PRIVATE_FLAG);
164	ksft_print_dbg_msg("m5:f2: %x\n", f2);
165}
166
167TEST_HARNESS_MAIN