[LTP] [PATCH v2] futex: regression test for take hugepages into account when generating futex_key

[LTP] [PATCH v2] futex: regression test for take hugepages into account when generating futex_key

[Li Wang]

v1 ---> v2:

	* Macro HUGE_SISE replaced by read_hugepagesise().

	* futex_wait() get a timeout parameter

	* SAFE_MMAP SAFE_MUNMAP() and pthread_join() been used.

	* Semaphore been added to do synchronization.

Signed-off-by: Li Wang <liwang@redhat.com>
---
 runtest/syscalls                               |   1 +
 testcases/kernel/syscalls/futex/Makefile       |   1 +
 testcases/kernel/syscalls/futex/futex_wake04.c | 193 +++++++++++++++++++++++++
 3 files changed, 195 insertions(+)
 create mode 100644 testcases/kernel/syscalls/futex/futex_wake04.c

diff --git a/runtest/syscalls b/runtest/syscalls
index 07bfc1e..1308536 100644
--- a/runtest/syscalls
+++ b/runtest/syscalls
@@ -1382,5 +1382,6 @@ futex_wait05 futex_wait05
 futex_wake01 futex_wake01
 futex_wake02 futex_wake02
 futex_wake03 futex_wake03
+futex_wake04 futex_wake04
 futex_wait_bitset01 futex_wait_bitset01
 futex_wait_bitset02 futex_wait_bitset02
diff --git a/testcases/kernel/syscalls/futex/Makefile b/testcases/kernel/syscalls/futex/Makefile
index d888734..6e72daf 100644
--- a/testcases/kernel/syscalls/futex/Makefile
+++ b/testcases/kernel/syscalls/futex/Makefile
@@ -22,6 +22,7 @@ futex_wait02: LDLIBS+=-lrt
 futex_wake03: LDLIBS+=-lrt
 futex_wait03: CFLAGS+=-pthread
 futex_wake02: CFLAGS+=-pthread
+futex_wake04: CFLAGS+=-pthread
 futex_wait05: LDLIBS+=-lrt
 futex_wait_bitset01: LDLIBS+=-lrt
 futex_wait_bitset02: LDLIBS+=-lrt
diff --git a/testcases/kernel/syscalls/futex/futex_wake04.c b/testcases/kernel/syscalls/futex/futex_wake04.c
new file mode 100644
index 0000000..78a52ff
--- /dev/null
+++ b/testcases/kernel/syscalls/futex/futex_wake04.c
@@ -0,0 +1,193 @@
+/*
+ * Copyright (C) 2015  Yi Zhang <wetpzy@gmail.com>
+ *                     Li Wang <liwang@redhat.com>
+ *
+ * Licensed under the GNU GPLv2 or later.
+ * 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 2 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, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+ /* DESCRIPTION:
+ *
+ *   It is a regression test for commit:
+ *   http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/
+ *   commit/?id=13d60f4
+ *
+ *   The implementation of futex doesn't produce unique keys for futexes
+ *   in shared huge pages, so threads waiting on different futexes may
+ *   end up on the same wait list. This results in incorrect threads being
+ *   woken by FUTEX_WAKE.
+ *
+ *   Needs to be run as root unless there are already enough huge pages available.
+ *   In the fail case, which happens in the CentOS-6.6 kernel (2.6.32-504.8.1),
+ *   the tests hangs until it times out after a 30-second wait.
+ *
+ */
+
+#include <stdio.h>
+#include <sys/mman.h>
+#include <fcntl.h>
+#include <pthread.h>
+#include <errno.h>
+#include <sys/time.h>
+#include <string.h>
+#include <semaphore.h>
+
+#include "test.h"
+#include "safe_macros.h"
+#include "futextest.h"
+
+#define PATH_MEMINFO "/proc/meminfo"
+#define PATH_NR_HUGEPAGES "/proc/sys/vm/nr_hugepages"
+
+const char *TCID = "futex_wake04";
+const int TST_TOTAL = 1;
+
+static futex_t *futex1, *futex2;
+
+static struct timespec to = {.tv_sec = 30, .tv_nsec = 0};
+
+static long orig_hugepages;
+
+static sem_t bin_sem;
+
+static void setup(void)
+{
+	tst_require_root(NULL);
+	tst_tmpdir();
+
+	SAFE_FILE_SCANF(NULL, PATH_NR_HUGEPAGES, "%ld", &orig_hugepages);
+	SAFE_FILE_PRINTF(NULL, PATH_NR_HUGEPAGES, "%d", 1);
+
+	TEST_PAUSE;
+}
+
+static void cleanup(void)
+{
+	SAFE_FILE_PRINTF(NULL, PATH_NR_HUGEPAGES, "%ld", orig_hugepages);
+
+	tst_rmdir();
+}
+
+static int read_hugepagesize(void)
+{
+	FILE *fp;
+	char line[BUFSIZ], buf[BUFSIZ];
+	int val;
+
+	fp = SAFE_FOPEN(cleanup, PATH_MEMINFO, "r");
+	while (fgets(line, BUFSIZ, fp) != NULL) {
+		if (sscanf(line, "%64s %d", buf, &val) == 2)
+			if (strcmp(buf, "Hugepagesize:") == 0) {
+				SAFE_FCLOSE(cleanup, fp);
+				return 1024 * val;
+			}
+	}
+
+	SAFE_FCLOSE(cleanup, fp);
+	tst_brkm(TBROK, NULL, "can't find \"%s\" in %s",
+			"Hugepagesize:", PATH_MEMINFO);
+}
+
+static void *wait_thread1(void *arg LTP_ATTRIBUTE_UNUSED)
+{
+	sem_post(&bin_sem);
+
+	futex_wait(futex1, *futex1, &to, 0);
+
+	return NULL;
+}
+
+static void *wait_thread2(void *arg LTP_ATTRIBUTE_UNUSED)
+{
+	int res;
+
+	sem_post(&bin_sem);
+
+	res = futex_wait(futex2, *futex2, &to, 0);
+	if (!res)
+		tst_resm(TPASS, "Hi hydra, thread2 awake!");
+	else
+		tst_resm(TFAIL, "Bug: wait_thread2 did not wake after 30 secs.");
+
+	return NULL;
+}
+
+static void wakeup_thread2(void)
+{
+	void *addr;
+	int hpsz, pgsz, res;
+	pthread_t th1, th2;
+
+	res = sem_init(&bin_sem, 0, 0);
+	if (res)
+		tst_brkm(TBROK, NULL, "Semaphore initialization failed.");
+
+	hpsz = read_hugepagesize();
+
+	/*allocate some shared memory*/
+	addr = SAFE_MMAP(NULL, NULL, hpsz, PROT_WRITE | PROT_READ,
+			MAP_SHARED | MAP_ANONYMOUS | MAP_HUGETLB, -1, 0);
+
+	pgsz = getpagesize();
+
+	/*apply the first subpage to futex1*/
+	futex1 = addr;
+	*futex1 = 0;
+	/*apply the second subpage to futex2*/
+	futex2 = (futex_t *)((char *)addr + pgsz);
+	*futex2 = 0;
+
+	/*thread1 block on futex1 first,then thread2 block on futex2*/
+	res = pthread_create(&th1, NULL, wait_thread1, NULL);
+	if (res) {
+		tst_brkm(TBROK, NULL, "pthread_create(): %s",
+				tst_strerrno(res));
+	}
+	sem_wait(&bin_sem);
+
+	res = pthread_create(&th2, NULL, wait_thread2, NULL);
+	if (res) {
+		tst_brkm(TBROK, NULL, "pthread_create(): %s",
+				tst_strerrno(res));
+	}
+	sem_wait(&bin_sem);
+
+	futex_wake(futex2, 1, 0);
+
+	res = pthread_join(th2, NULL);
+	if (res)
+		tst_brkm(TBROK, NULL, "pthread_join(): %s", tst_strerrno(res));
+
+	res = pthread_join(th1, NULL);
+	if (res)
+		tst_brkm(TBROK, NULL, "pthread_join(): %s", tst_strerrno(res));
+
+	sem_destroy(&bin_sem);
+	SAFE_MUNMAP(NULL, addr, hpsz);
+}
+
+int main(int argc, char *argv[])
+{
+	int lc;
+
+	tst_parse_opts(argc, argv, NULL, NULL);
+
+	setup();
+
+	for (lc = 0; TEST_LOOPING(lc); lc++)
+		wakeup_thread2();
+
+	cleanup();
+	tst_exit();
+}
-- 
1.8.3.1


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Re: [LTP] [PATCH v2] futex: regression test for take hugepages into account when generating futex_key

[Li Wang]

Hi, 

Ping~
Any comments?

-- 
Regards, 
Li Wang 
Email: liwang@redhat.com 


----- Original Message -----
> v1 ---> v2:
> 
> 	* Macro HUGE_SISE replaced by read_hugepagesise().
> 
> 	* futex_wait() get a timeout parameter
> 
> 	* SAFE_MMAP SAFE_MUNMAP() and pthread_join() been used.
> 
> 	* Semaphore been added to do synchronization.
> 
> Signed-off-by: Li Wang <liwang@redhat.com>
> ---
>  runtest/syscalls                               |   1 +
>  testcases/kernel/syscalls/futex/Makefile       |   1 +
>  testcases/kernel/syscalls/futex/futex_wake04.c | 193
>  +++++++++++++++++++++++++
>  3 files changed, 195 insertions(+)
>  create mode 100644 testcases/kernel/syscalls/futex/futex_wake04.c
> 
> diff --git a/runtest/syscalls b/runtest/syscalls
> index 07bfc1e..1308536 100644
> --- a/runtest/syscalls
> +++ b/runtest/syscalls
> @@ -1382,5 +1382,6 @@ futex_wait05 futex_wait05
>  futex_wake01 futex_wake01
>  futex_wake02 futex_wake02
>  futex_wake03 futex_wake03
> +futex_wake04 futex_wake04
>  futex_wait_bitset01 futex_wait_bitset01
>  futex_wait_bitset02 futex_wait_bitset02
> diff --git a/testcases/kernel/syscalls/futex/Makefile
> b/testcases/kernel/syscalls/futex/Makefile
> index d888734..6e72daf 100644
> --- a/testcases/kernel/syscalls/futex/Makefile
> +++ b/testcases/kernel/syscalls/futex/Makefile
> @@ -22,6 +22,7 @@ futex_wait02: LDLIBS+=-lrt
>  futex_wake03: LDLIBS+=-lrt
>  futex_wait03: CFLAGS+=-pthread
>  futex_wake02: CFLAGS+=-pthread
> +futex_wake04: CFLAGS+=-pthread
>  futex_wait05: LDLIBS+=-lrt
>  futex_wait_bitset01: LDLIBS+=-lrt
>  futex_wait_bitset02: LDLIBS+=-lrt
> diff --git a/testcases/kernel/syscalls/futex/futex_wake04.c
> b/testcases/kernel/syscalls/futex/futex_wake04.c
> new file mode 100644
> index 0000000..78a52ff
> --- /dev/null
> +++ b/testcases/kernel/syscalls/futex/futex_wake04.c
> @@ -0,0 +1,193 @@
> +/*
> + * Copyright (C) 2015  Yi Zhang <wetpzy@gmail.com>
> + *                     Li Wang <liwang@redhat.com>
> + *
> + * Licensed under the GNU GPLv2 or later.
> + * 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 2 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, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301
> USA
> + */
> + /* DESCRIPTION:
> + *
> + *   It is a regression test for commit:
> + *   http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/
> + *   commit/?id=13d60f4
> + *
> + *   The implementation of futex doesn't produce unique keys for futexes
> + *   in shared huge pages, so threads waiting on different futexes may
> + *   end up on the same wait list. This results in incorrect threads being
> + *   woken by FUTEX_WAKE.
> + *
> + *   Needs to be run as root unless there are already enough huge pages
> available.
> + *   In the fail case, which happens in the CentOS-6.6 kernel
> (2.6.32-504.8.1),
> + *   the tests hangs until it times out after a 30-second wait.
> + *
> + */
> +
> +#include <stdio.h>
> +#include <sys/mman.h>
> +#include <fcntl.h>
> +#include <pthread.h>
> +#include <errno.h>
> +#include <sys/time.h>
> +#include <string.h>
> +#include <semaphore.h>
> +
> +#include "test.h"
> +#include "safe_macros.h"
> +#include "futextest.h"
> +
> +#define PATH_MEMINFO "/proc/meminfo"
> +#define PATH_NR_HUGEPAGES "/proc/sys/vm/nr_hugepages"
> +
> +const char *TCID = "futex_wake04";
> +const int TST_TOTAL = 1;
> +
> +static futex_t *futex1, *futex2;
> +
> +static struct timespec to = {.tv_sec = 30, .tv_nsec = 0};
> +
> +static long orig_hugepages;
> +
> +static sem_t bin_sem;
> +
> +static void setup(void)
> +{
> +	tst_require_root(NULL);
> +	tst_tmpdir();
> +
> +	SAFE_FILE_SCANF(NULL, PATH_NR_HUGEPAGES, "%ld", &orig_hugepages);
> +	SAFE_FILE_PRINTF(NULL, PATH_NR_HUGEPAGES, "%d", 1);
> +
> +	TEST_PAUSE;
> +}
> +
> +static void cleanup(void)
> +{
> +	SAFE_FILE_PRINTF(NULL, PATH_NR_HUGEPAGES, "%ld", orig_hugepages);
> +
> +	tst_rmdir();
> +}
> +
> +static int read_hugepagesize(void)
> +{
> +	FILE *fp;
> +	char line[BUFSIZ], buf[BUFSIZ];
> +	int val;
> +
> +	fp = SAFE_FOPEN(cleanup, PATH_MEMINFO, "r");
> +	while (fgets(line, BUFSIZ, fp) != NULL) {
> +		if (sscanf(line, "%64s %d", buf, &val) == 2)
> +			if (strcmp(buf, "Hugepagesize:") == 0) {
> +				SAFE_FCLOSE(cleanup, fp);
> +				return 1024 * val;
> +			}
> +	}
> +
> +	SAFE_FCLOSE(cleanup, fp);
> +	tst_brkm(TBROK, NULL, "can't find \"%s\" in %s",
> +			"Hugepagesize:", PATH_MEMINFO);
> +}
> +
> +static void *wait_thread1(void *arg LTP_ATTRIBUTE_UNUSED)
> +{
> +	sem_post(&bin_sem);
> +
> +	futex_wait(futex1, *futex1, &to, 0);
> +
> +	return NULL;
> +}
> +
> +static void *wait_thread2(void *arg LTP_ATTRIBUTE_UNUSED)
> +{
> +	int res;
> +
> +	sem_post(&bin_sem);
> +
> +	res = futex_wait(futex2, *futex2, &to, 0);
> +	if (!res)
> +		tst_resm(TPASS, "Hi hydra, thread2 awake!");
> +	else
> +		tst_resm(TFAIL, "Bug: wait_thread2 did not wake after 30 secs.");
> +
> +	return NULL;
> +}
> +
> +static void wakeup_thread2(void)
> +{
> +	void *addr;
> +	int hpsz, pgsz, res;
> +	pthread_t th1, th2;
> +
> +	res = sem_init(&bin_sem, 0, 0);
> +	if (res)
> +		tst_brkm(TBROK, NULL, "Semaphore initialization failed.");
> +
> +	hpsz = read_hugepagesize();
> +
> +	/*allocate some shared memory*/
> +	addr = SAFE_MMAP(NULL, NULL, hpsz, PROT_WRITE | PROT_READ,
> +			MAP_SHARED | MAP_ANONYMOUS | MAP_HUGETLB, -1, 0);
> +
> +	pgsz = getpagesize();
> +
> +	/*apply the first subpage to futex1*/
> +	futex1 = addr;
> +	*futex1 = 0;
> +	/*apply the second subpage to futex2*/
> +	futex2 = (futex_t *)((char *)addr + pgsz);
> +	*futex2 = 0;
> +
> +	/*thread1 block on futex1 first,then thread2 block on futex2*/
> +	res = pthread_create(&th1, NULL, wait_thread1, NULL);
> +	if (res) {
> +		tst_brkm(TBROK, NULL, "pthread_create(): %s",
> +				tst_strerrno(res));
> +	}
> +	sem_wait(&bin_sem);
> +
> +	res = pthread_create(&th2, NULL, wait_thread2, NULL);
> +	if (res) {
> +		tst_brkm(TBROK, NULL, "pthread_create(): %s",
> +				tst_strerrno(res));
> +	}
> +	sem_wait(&bin_sem);
> +
> +	futex_wake(futex2, 1, 0);
> +
> +	res = pthread_join(th2, NULL);
> +	if (res)
> +		tst_brkm(TBROK, NULL, "pthread_join(): %s", tst_strerrno(res));
> +
> +	res = pthread_join(th1, NULL);
> +	if (res)
> +		tst_brkm(TBROK, NULL, "pthread_join(): %s", tst_strerrno(res));
> +
> +	sem_destroy(&bin_sem);
> +	SAFE_MUNMAP(NULL, addr, hpsz);
> +}
> +
> +int main(int argc, char *argv[])
> +{
> +	int lc;
> +
> +	tst_parse_opts(argc, argv, NULL, NULL);
> +
> +	setup();
> +
> +	for (lc = 0; TEST_LOOPING(lc); lc++)
> +		wakeup_thread2();
> +
> +	cleanup();
> +	tst_exit();
> +}
> --
> 1.8.3.1
> 
> 
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Re: [LTP] [PATCH v2] futex: regression test for take hugepages into account when generating futex_key

[Cyril Hrubis]

Hi!
> Ping~
> Any comments?

Sorry for the delay. Looks good, but the race codintion with the
semaphores is still possible, although unlikely.

Because the semaphore is posted before the second thread is locked on
the futex, there is slight possibility that the futex_wake() (from the
main thread) is called before the second thread sleeps in the futex
which will cause the testcase to fail.

I will isolate the function to assert that threads are sleeping in
kernel from the futex testcase and change this test to make use of it
and commit it.

-- 
Cyril Hrubis
chrubis@suse.cz

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Re: [LTP] [PATCH v2] futex: regression test for take hugepages into account when generating futex_key

[Cyril Hrubis]

Hi!
And I've pushed the test with following changes.

* Use the wait_for_threads() function instead of semaphores

* Wake the futex on first thread before the first thread is joined
  (otherwise the test waits for 30 seconds doing nothing before it
   reports success)

* Do not fail the test if mmaping hugepage fails with ENOMEM
  this may happen on machines that run for days without reboot
  and memory gets fragmented too much
  (this is no TCONF)

Thanks.

-- 
Cyril Hrubis
chrubis@suse.cz

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