[PATCH v2] tests: posix: use cpu clock for sleep

[Yury Khrustalev]

On some emulated targets sleep may result in inconsistent wait
times which will lead to the failure of the tst-chmod test.

To account for this we use the CLOCK_PROCESS_CPUTIME_ID clock ID
while also consuming CPU time by repeatedly calling clock_gettime.

---
Passes regression on aarch64 and x86. OK for trunk?
Base commit: 0d0e439439

Changes in v2:
 - Take nanoseconds into accout to make sleep more accurate.
 - v1: https://inbox.sourceware.org/libc-alpha/20260202153535.1368528-1-yury.khrustalev@arm.com/

---
 posix/tst-chmod.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/posix/tst-chmod.c b/posix/tst-chmod.c
index 80a69dddd4..738e9aedd2 100644
--- a/posix/tst-chmod.c
+++ b/posix/tst-chmod.c
@@ -26,6 +26,7 @@
 #include <string.h>
 #include <unistd.h>
 #include <sys/stat.h>
+#include <time.h>
 
 #include <support/xunistd.h>
 
@@ -37,6 +38,21 @@
     goto fail;								      \
   } while (0)
 
+/* On some emulated targets sleep may result in inconsistent wait
+   times which will lead to the failure of this test.  To account
+   for this we use the CLOCK_PROCESS_CPUTIME_ID clock ID while
+   also consuming CPU time by repeatedly calling clock_gettime. */
+static void
+test_sleep (signed long seconds)
+{
+  struct timespec ts;
+  clock_gettime (CLOCK_PROCESS_CPUTIME_ID, &ts);
+  signed long end = ts.tv_sec + seconds;
+  signed long end_ns = ts.tv_nsec;
+  while (ts.tv_sec < end || (ts.tv_sec == end && ts.tv_nsec < end_ns))
+    clock_gettime (CLOCK_PROCESS_CPUTIME_ID, &ts);
+}
+
 static int
 do_test (int argc, char *argv[])
 {
@@ -108,7 +124,7 @@ do_test (int argc, char *argv[])
     }
 
   /* We have to wait for a second to make sure the ctime changes.  */
-  sleep (1);
+  test_sleep (1);
 
   /* Remove all access rights from the directory.  */
   if (chmod (testdir, 0) != 0)
@@ -236,7 +252,7 @@ do_test (int argc, char *argv[])
   /* We are now in the directory above the one we create the test
      directory in.  */
 
-  sleep (1);
+  test_sleep (1);
   snprintf (buf, buflen, "./%s/../%s/file",
 	    basename (testdir), basename (testdir));
   if (chmod (buf, 0600) != 0)
-- 
2.47.3