* [PATCH 1/2] docs: ntsync: align ioctl names and struct layouts with uapi
2026-07-20 17:54 [PATCH 0/2] ntsync: docs uAPI fixup and timens selftest Iván Ezequiel Rodriguez
@ 2026-07-20 17:54 ` Iván Ezequiel Rodriguez
2026-07-20 17:54 ` [PATCH 2/2] selftests: ntsync: test absolute MONOTONIC waits under time namespaces Iván Ezequiel Rodriguez
1 sibling, 0 replies; 3+ messages in thread
From: Iván Ezequiel Rodriguez @ 2026-07-20 17:54 UTC (permalink / raw)
To: Elizabeth Figura
Cc: Jonathan Corbet, linux-doc, Shuah Khan, linux-kselftest,
linux-kernel, Iván Ezequiel Rodriguez
The uAPI documentation used outdated or conceptual ioctl macro names
and listed ntsync_event_args / ntsync_wait_args fields in the wrong
order. Match include/uapi/linux/ntsync.h and note that absolute
MONOTONIC timeouts are interpreted in the caller's time namespace.
Signed-off-by: Iván Ezequiel Rodriguez <ivanrwcm25@gmail.com>
---
Documentation/userspace-api/ntsync.rst | 33 +++++++++++++-------------
1 file changed, 17 insertions(+), 16 deletions(-)
diff --git a/Documentation/userspace-api/ntsync.rst b/Documentation/userspace-api/ntsync.rst
index 25e7c4aef968..a778016feb87 100644
--- a/Documentation/userspace-api/ntsync.rst
+++ b/Documentation/userspace-api/ntsync.rst
@@ -83,18 +83,18 @@ structures used in ioctl calls::
};
struct ntsync_event_args {
- __u32 signaled;
__u32 manual;
+ __u32 signaled;
};
struct ntsync_wait_args {
__u64 timeout;
__u64 objs;
__u32 count;
- __u32 owner;
__u32 index;
- __u32 alert;
__u32 flags;
+ __u32 owner;
+ __u32 alert;
__u32 pad;
};
@@ -152,7 +152,7 @@ The ioctls on the device file are as follows:
The ioctls on the individual objects are as follows:
-.. c:macro:: NTSYNC_IOC_SEM_POST
+.. c:macro:: NTSYNC_IOC_SEM_RELEASE
Post to a semaphore object. Takes a pointer to a 32-bit integer,
which on input holds the count to be added to the semaphore, and on
@@ -186,7 +186,7 @@ The ioctls on the individual objects are as follows:
unowned and signaled, and eligible threads waiting on it will be
woken as appropriate.
-.. c:macro:: NTSYNC_IOC_SET_EVENT
+.. c:macro:: NTSYNC_IOC_EVENT_SET
Signal an event object. Takes a pointer to a 32-bit integer, which on
output contains the previous state of the event.
@@ -194,12 +194,12 @@ The ioctls on the individual objects are as follows:
Eligible threads will be woken, and auto-reset events will be
designaled appropriately.
-.. c:macro:: NTSYNC_IOC_RESET_EVENT
+.. c:macro:: NTSYNC_IOC_EVENT_RESET
Designal an event object. Takes a pointer to a 32-bit integer, which
on output contains the previous state of the event.
-.. c:macro:: NTSYNC_IOC_PULSE_EVENT
+.. c:macro:: NTSYNC_IOC_EVENT_PULSE
Wake threads waiting on an event object while leaving it in an
unsignaled state. Takes a pointer to a 32-bit integer, which on
@@ -213,7 +213,7 @@ The ioctls on the individual objects are as follows:
afterwards, and a simultaneous read operation will always report the
event as unsignaled.
-.. c:macro:: NTSYNC_IOC_READ_SEM
+.. c:macro:: NTSYNC_IOC_SEM_READ
Read the current state of a semaphore object. Takes a pointer to
struct :c:type:`ntsync_sem_args`, which is used as follows:
@@ -225,7 +225,7 @@ The ioctls on the individual objects are as follows:
* - ``max``
- On output, contains the maximum count of the semaphore.
-.. c:macro:: NTSYNC_IOC_READ_MUTEX
+.. c:macro:: NTSYNC_IOC_MUTEX_READ
Read the current state of a mutex object. Takes a pointer to struct
:c:type:`ntsync_mutex_args`, which is used as follows:
@@ -242,7 +242,7 @@ The ioctls on the individual objects are as follows:
``EOWNERDEAD``. In this case, ``count`` and ``owner`` are set to
zero.
-.. c:macro:: NTSYNC_IOC_READ_EVENT
+.. c:macro:: NTSYNC_IOC_EVENT_READ
Read the current state of an event object. Takes a pointer to struct
:c:type:`ntsync_event_args`, which is used as follows:
@@ -255,7 +255,7 @@ The ioctls on the individual objects are as follows:
- On output, contains 1 if the event is a manual-reset event,
and 0 otherwise.
-.. c:macro:: NTSYNC_IOC_KILL_OWNER
+.. c:macro:: NTSYNC_IOC_MUTEX_KILL
Mark a mutex as unowned and abandoned if it is owned by the given
owner. Takes an input-only pointer to a 32-bit integer denoting the
@@ -276,11 +276,12 @@ The ioctls on the individual objects are as follows:
* - ``timeout``
- Absolute timeout in nanoseconds. If ``NTSYNC_WAIT_REALTIME``
is set, the timeout is measured against the REALTIME clock;
- otherwise it is measured against the MONOTONIC clock. If the
- timeout is equal to or earlier than the current time, the
- function returns immediately without sleeping. If ``timeout``
- is U64_MAX, the function will sleep until an object is
- signaled, and will not fail with ``ETIMEDOUT``.
+ otherwise it is measured against the MONOTONIC clock in the
+ caller's time namespace. If the timeout is equal to or earlier
+ than the current time, the function returns immediately
+ without sleeping. If ``timeout`` is U64_MAX, the function will
+ sleep until an object is signaled, and will not fail with
+ ``ETIMEDOUT``.
* - ``objs``
- Pointer to an array of ``count`` file descriptors
(specified as an integer so that the structure has the same
--
2.43.0
^ permalink raw reply related [flat|nested] 3+ messages in thread* [PATCH 2/2] selftests: ntsync: test absolute MONOTONIC waits under time namespaces
2026-07-20 17:54 [PATCH 0/2] ntsync: docs uAPI fixup and timens selftest Iván Ezequiel Rodriguez
2026-07-20 17:54 ` [PATCH 1/2] docs: ntsync: align ioctl names and struct layouts with uapi Iván Ezequiel Rodriguez
@ 2026-07-20 17:54 ` Iván Ezequiel Rodriguez
1 sibling, 0 replies; 3+ messages in thread
From: Iván Ezequiel Rodriguez @ 2026-07-20 17:54 UTC (permalink / raw)
To: Elizabeth Figura
Cc: Jonathan Corbet, linux-doc, Shuah Khan, linux-kselftest,
linux-kernel, Iván Ezequiel Rodriguez, Maoyi Xie
Cover the timens conversion in ntsync_schedule(): with a negative
CLOCK_MONOTONIC offset, a 100 ms absolute wait must not return
immediately against the host clock.
Suggested-by: Maoyi Xie <maoyixie.tju@gmail.com>
Signed-off-by: Iván Ezequiel Rodriguez <ivanrwcm25@gmail.com>
---
.../testing/selftests/drivers/ntsync/ntsync.c | 87 +++++++++++++++++++
1 file changed, 87 insertions(+)
diff --git a/tools/testing/selftests/drivers/ntsync/ntsync.c b/tools/testing/selftests/drivers/ntsync/ntsync.c
index e6a37214aa46..ce000ff41535 100644
--- a/tools/testing/selftests/drivers/ntsync/ntsync.c
+++ b/tools/testing/selftests/drivers/ntsync/ntsync.c
@@ -8,12 +8,18 @@
#define _GNU_SOURCE
#include <sys/ioctl.h>
#include <sys/stat.h>
+#include <sys/wait.h>
#include <fcntl.h>
+#include <sched.h>
#include <time.h>
#include <pthread.h>
#include <linux/ntsync.h>
#include "kselftest_harness.h"
+#ifndef CLONE_NEWTIME
+#define CLONE_NEWTIME 0x00000080
+#endif
+
static int read_sem_state(int sem, __u32 *count, __u32 *max)
{
struct ntsync_sem_args args;
@@ -1340,4 +1346,85 @@ TEST(stress_wait)
close(stress_device);
}
+/*
+ * Absolute MONOTONIC timeouts must honour the caller's time namespace.
+ * With a negative monotonic offset, a 100 ms wait must still take ~100 ms
+ * of namespace time (not return immediately against the host clock).
+ */
+TEST(wait_any_monotonic_timens)
+{
+ struct ntsync_sem_args sem_args = {0};
+ struct ntsync_wait_args wait_args = {0};
+ struct timespec start, end;
+ char buf[64];
+ __u64 elapsed_ns;
+ int fd, offset_fd, sem, ret, status, len;
+ pid_t pid;
+
+ if (access("/proc/self/ns/time", F_OK))
+ SKIP(return, "Time namespaces are not supported");
+
+ fd = open("/dev/ntsync", O_CLOEXEC | O_RDONLY);
+ if (fd < 0)
+ SKIP(return, "/dev/ntsync is not available");
+
+ ret = unshare(CLONE_NEWTIME);
+ if (ret) {
+ close(fd);
+ if (errno == EPERM)
+ SKIP(return, "need CAP_SYS_ADMIN for CLONE_NEWTIME");
+ ASSERT_EQ(0, ret);
+ }
+
+ len = snprintf(buf, sizeof(buf), "%d %d 0", CLOCK_MONOTONIC, -10);
+ offset_fd = open("/proc/self/timens_offsets", O_WRONLY);
+ ASSERT_LE(0, offset_fd);
+ ASSERT_EQ(len, write(offset_fd, buf, len));
+ close(offset_fd);
+
+ pid = fork();
+ ASSERT_LE(0, pid);
+ if (!pid) {
+ int obj;
+
+ sem_args.count = 0;
+ sem_args.max = 1;
+ sem = ioctl(fd, NTSYNC_IOC_CREATE_SEM, &sem_args);
+ if (sem < 0)
+ _exit(1);
+
+ obj = sem;
+ wait_args.timeout = get_abs_timeout(100);
+ wait_args.objs = (uintptr_t)&obj;
+ wait_args.count = 1;
+ wait_args.owner = 123;
+ wait_args.index = 0xdeadbeef;
+
+ if (clock_gettime(CLOCK_MONOTONIC, &start))
+ _exit(2);
+ ret = ioctl(fd, NTSYNC_IOC_WAIT_ANY, &wait_args);
+ if (clock_gettime(CLOCK_MONOTONIC, &end))
+ _exit(2);
+
+ if (ret != -1 || errno != ETIMEDOUT)
+ _exit(3);
+
+ elapsed_ns = (end.tv_sec - start.tv_sec) * 1000000000ULL +
+ (end.tv_nsec - start.tv_nsec);
+ /* Without timens conversion this returns in ~0 ms. */
+ if (elapsed_ns < 50 * 1000000ULL)
+ _exit(4);
+ if (elapsed_ns > 1000 * 1000000ULL)
+ _exit(5);
+
+ _exit(0);
+ }
+
+ ASSERT_EQ(pid, waitpid(pid, &status, 0));
+ EXPECT_TRUE(WIFEXITED(status));
+ EXPECT_EQ(0, WEXITSTATUS(status));
+
+ close(fd);
+}
+
TEST_HARNESS_MAIN
--
2.43.0
^ permalink raw reply related [flat|nested] 3+ messages in thread