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utimensat-tests, etc.: try to fix some races

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Problem reported by Bernhard Voelker in
<http://lists.gnu.org/archive/html/bug-gnulib/2013-04/msg00071.html>.
I don't know whether this patch fixes that race condition, but it
fixes *some* race conditions, so it should be a win.
* modules/chown-tests (Depends-on):
* modules/fchownat-tests (Depends-on):
* modules/fdutimensat-tests (Depends-on):
* modules/futimens-tests (Depends-on):
* modules/lchown-tests (Depends-on):
* modules/stat-time-tests (Depends-on):
* modules/utimens-tests (Depends-on):
* modules/utimensat-tests (Depends-on):
Depend on nanosleep, not usleep.
* modules/chown-tests (test_chown_LDADD):
* modules/lchown-tests (test_lchown_LDADD):
* modules/stat-time-tests (test_stat_time_LDADD):
New macro.
* modules/fchownat-tests (test_fchownat_LDADD):
* modules/fdutimensat-tests (test_fdutimensat_LDADD):
* modules/futimens-tests (test_futimens_LDADD):
* modules/utimens-tests (test_utimens_LDADD):
* modules/utimensat-tests (test_utimensat_LDADD):
Add $(LIB_NANOSLEEP).
* modules/stat-time-tests (Files): Add tests/nap.h.
* tests/nap.h: Include <limits.h>, for INT_MAX.
(lt_mtime): Remove.
(diff_timespec): New function.
(get_stat): Rename from get_mtime.  All callers changed.
(nap_works): Determine the needed delay by inspecting the
file system's timestamp jumps; this should be more reliable.
Look at both mtime and ctime, and take the maximum of the two jumps.
(nap_works, guess_delay):
Return a nanosecond cound, not a microsecond count.
All callers changed.
(nap_works, nap): Use nanosleep, not usleep.  Check for nanosleep
failure.
(nap): Multiply the guess by 1.125, to accommodate the case where
the file system's clock is a bit slower than nanosleep's clock.
* tests/test-stat-time.c (BASE): New macro.
Include nap.h.
(nap): Remove; nap.h now defines this.  This removes a duplicate
implementation of 'nap'.
This commit is contained in:
Paul Eggert
2013-04-30 23:14:19 -07:00
parent 4bbfd28498
commit 5191133e01
11 changed files with 141 additions and 96 deletions
Download Patch File Download Diff File Expand all files Collapse all files

44
ChangeLog
View File

@@ -1,5 +1,49 @@
2013-04-30 Paul Eggert <eggert@cs.ucla.edu>
utimensat-tests, etc.: try to fix some races
Problem reported by Bernhard Voelker in
<http://lists.gnu.org/archive/html/bug-gnulib/2013-04/msg00071.html>.
I don't know whether this patch fixes that race condition, but it
fixes *some* race conditions, so it should be a win.
* modules/chown-tests (Depends-on):
* modules/fchownat-tests (Depends-on):
* modules/fdutimensat-tests (Depends-on):
* modules/futimens-tests (Depends-on):
* modules/lchown-tests (Depends-on):
* modules/stat-time-tests (Depends-on):
* modules/utimens-tests (Depends-on):
* modules/utimensat-tests (Depends-on):
Depend on nanosleep, not usleep.
* modules/chown-tests (test_chown_LDADD):
* modules/lchown-tests (test_lchown_LDADD):
* modules/stat-time-tests (test_stat_time_LDADD):
New macro.
* modules/fchownat-tests (test_fchownat_LDADD):
* modules/fdutimensat-tests (test_fdutimensat_LDADD):
* modules/futimens-tests (test_futimens_LDADD):
* modules/utimens-tests (test_utimens_LDADD):
* modules/utimensat-tests (test_utimensat_LDADD):
Add $(LIB_NANOSLEEP).
* modules/stat-time-tests (Files): Add tests/nap.h.
* tests/nap.h: Include <limits.h>, for INT_MAX.
(lt_mtime): Remove.
(diff_timespec): New function.
(get_stat): Rename from get_mtime. All callers changed.
(nap_works): Determine the needed delay by inspecting the
file system's timestamp jumps; this should be more reliable.
Look at both mtime and ctime, and take the maximum of the two jumps.
(nap_works, guess_delay):
Return a nanosecond cound, not a microsecond count.
All callers changed.
(nap_works, nap): Use nanosleep, not usleep. Check for nanosleep
failure.
(nap): Multiply the guess by 1.125, to accommodate the case where
the file system's clock is a bit slower than nanosleep's clock.
* tests/test-stat-time.c (BASE): New macro.
Include nap.h.
(nap): Remove; nap.h now defines this. This removes a duplicate
implementation of 'nap'.
utimens, utimensat: work around Solaris UTIME_OMIT bug
Solaris 11.1 and Solaris 10 have the same UTIME_OMIT bug that
Linux kernel 2.6.32 does. Work around it in the same way.

3
modules/chown-tests
View File

@@ -9,7 +9,7 @@ Depends-on:
ignore-value
lstat
mgetgroups
usleep
nanosleep
stat-time
stdbool
symlink
@@ -20,3 +20,4 @@ AC_CHECK_FUNCS_ONCE([getegid])
Makefile.am:
TESTS += test-chown
check_PROGRAMS += test-chown
test_chown_LDADD = $(LDADD) $(LIB_NANOSLEEP)

4
modules/fchownat-tests
View File

@@ -9,9 +9,9 @@ tests/macros.h
Depends-on:
ignore-value
mgetgroups
nanosleep
openat-h
progname
usleep
stat-time
symlink
@@ -21,4 +21,4 @@ AC_CHECK_FUNCS_ONCE([getegid])
Makefile.am:
TESTS += test-fchownat
check_PROGRAMS += test-fchownat
test_fchownat_LDADD = $(LDADD) @LIBINTL@
test_fchownat_LDADD = $(LDADD) $(LIB_NANOSLEEP) @LIBINTL@

5
modules/fdutimensat-tests
View File

@@ -10,10 +10,10 @@ tests/macros.h
Depends-on:
fcntl-h
ignore-value
nanosleep
openat
timespec
dup
usleep
utimecmp
configure.ac:
@@ -21,4 +21,5 @@ configure.ac:
Makefile.am:
TESTS += test-fdutimensat
check_PROGRAMS += test-fdutimensat
test_fdutimensat_LDADD = $(LDADD) $(LIB_CLOCK_GETTIME) @LIBINTL@
test_fdutimensat_LDADD = $(LDADD) $(LIB_CLOCK_GETTIME) \
$(LIB_NANOSLEEP) @LIBINTL@

4
modules/futimens-tests
View File

@@ -10,9 +10,9 @@ Depends-on:
gettext
fcntl-h
ignore-value
nanosleep
timespec
dup
usleep
utimecmp
configure.ac:
@@ -20,4 +20,4 @@ configure.ac:
Makefile.am:
TESTS += test-futimens
check_PROGRAMS += test-futimens
test_futimens_LDADD = $(LDADD) $(LIB_CLOCK_GETTIME) @LIBINTL@
test_futimens_LDADD = $(LDADD) $(LIB_CLOCK_GETTIME) $(LIB_NANOSLEEP) @LIBINTL@

3
modules/lchown-tests
View File

@@ -8,7 +8,7 @@ tests/macros.h
Depends-on:
ignore-value
mgetgroups
usleep
nanosleep
stat-time
stdbool
symlink
@@ -19,3 +19,4 @@ AC_CHECK_FUNCS_ONCE([getegid])
Makefile.am:
TESTS += test-lchown
check_PROGRAMS += test-lchown
test_lchown_LDADD = $(LDADD) $(LIB_NANOSLEEP)

4
modules/stat-time-tests
View File

@@ -1,13 +1,15 @@
Files:
tests/test-stat-time.c
tests/macros.h
tests/nap.h
Depends-on:
nanosleep
time
usleep
configure.ac:
Makefile.am:
TESTS += test-stat-time
check_PROGRAMS += test-stat-time
test_stat_time_LDADD = $(LDADD) $(LIB_NANOSLEEP)

4
modules/utimens-tests
View File

@@ -11,9 +11,9 @@ Depends-on:
dup
gettext
ignore-value
nanosleep
symlink
timespec
usleep
utimecmp
configure.ac:
@@ -21,4 +21,4 @@ configure.ac:
Makefile.am:
TESTS += test-utimens
check_PROGRAMS += test-utimens
test_utimens_LDADD = $(LDADD) $(LIB_CLOCK_GETTIME) @LIBINTL@
test_utimens_LDADD = $(LDADD) $(LIB_CLOCK_GETTIME) $(LIB_NANOSLEEP) @LIBINTL@

4
modules/utimensat-tests
View File

@@ -9,8 +9,8 @@ tests/macros.h
Depends-on:
ignore-value
nanosleep
timespec
usleep
utimecmp
configure.ac:
@@ -18,4 +18,4 @@ configure.ac:
Makefile.am:
TESTS += test-utimensat
check_PROGRAMS += test-utimensat
test_utimensat_LDADD = $(LDADD) $(LIB_CLOCK_GETTIME) @LIBINTL@
test_utimensat_LDADD = $(LDADD) $(LIB_CLOCK_GETTIME) $(LIB_NANOSLEEP) @LIBINTL@

117
tests/nap.h
View File

@@ -19,19 +19,33 @@
#ifndef GLTEST_NAP_H
# define GLTEST_NAP_H
static int
lt_mtime (struct stat const *a, struct stat const *b)
{
time_t as = a->st_mtime;
time_t bs = b->st_mtime;
int ans = get_stat_mtime_ns (a);
int bns = get_stat_mtime_ns (b);
# include <limits.h>
return as < bs || (as == bs && ans < bns);
/* Return A - B, in ns.
Return 0 if the true result would be negative.
Return INT_MAX if the true result would be greater than INT_MAX. */
static int
diff_timespec (struct timespec a, struct timespec b)
{
time_t as = a.tv_sec;
time_t bs = b.tv_sec;
int ans = a.tv_nsec;
int bns = b.tv_nsec;
if (! (bs < as || (bs == as && bns < ans)))
return 0;
if (as - bs <= INT_MAX / 1000000000)
{
int sdiff = (as - bs) * 1000000000;
int usdiff = ans - bns;
if (usdiff < INT_MAX - sdiff)
return sdiff + usdiff;
}
return INT_MAX;
}
static void
get_mtime (int fd, struct stat *st, int do_write)
get_stat (int fd, struct stat *st, int do_write)
{
if (do_write)
ASSERT (write (fd, "\n", 1) == 1);
@@ -39,50 +53,61 @@ get_mtime (int fd, struct stat *st, int do_write)
}
/* Given a file whose descriptor is FD, see whether delaying by DELAY
microseconds causes a change in a file's time stamp. If the time
stamps differ, repeat the test one more time, in case we crossed a
quantization boundary on a file system with lower resolution. *ST
is the file's status, recently gotten. Update *ST to reflect the
latest status gotten. */
nanoseconds causes a change in a file's time stamp. *ST is the
file's status, recently gotten. Update *ST to reflect the latest
status gotten. If successful, return the needed delay, in
nanoseconds as determined by the observed time stamps; this may be
greater than DELAY if we crossed a quantization boundary. If
unsuccessful, return 0. */
static int
nap_works (int fd, int delay, struct stat *st)
{
struct stat old_st;
old_st = *st;
usleep (delay);
get_mtime (fd, st, 1);
if (! lt_mtime (&old_st, st))
return 0;
old_st = *st;
usleep (delay);
get_mtime (fd, st, 1);
return lt_mtime (&old_st, st);
struct stat old_st = *st;
struct timespec delay_spec;
int cdiff, mdiff;
delay_spec.tv_sec = delay / 1000000000;
delay_spec.tv_nsec = delay % 1000000000;
ASSERT (nanosleep (&delay_spec, 0) == 0);
get_stat (fd, st, 1);
/* Return the greater of the ctime and the mtime differences, or
zero if it cannot be determined, or INT_MAX if either overflows. */
cdiff = diff_timespec (get_stat_ctime (st), get_stat_ctime (&old_st));
if (cdiff != 0)
{
mdiff = diff_timespec (get_stat_mtime (st), get_stat_mtime (&old_st));
if (mdiff != 0)
return cdiff < mdiff ? mdiff : cdiff;
}
return 0;
}
static int
guess_delay (void)
{
/* Try a 1-microsecond sleep first, for speed. If that doesn't
work, try a 1 ms sleep; that should work with ext. If it doesn't
work, try a 20 ms sleep. xfs has a quantization of about 10
/* Try a 1-ns sleep first, for speed. If that doesn't work, try 100
ns, 1 microsecond, 1 ms, etc. xfs has a quantization of about 10
milliseconds, even though it has a granularity of 1 nanosecond,
and NTFS has a default quantization of 15.25 milliseconds, even
though it has a granularity of 100 nanoseconds, so 20 ms is a
though it has a granularity of 100 nanoseconds, so 15.25 ms is a
good quantization to try. If that doesn't work, try 1 second.
The worst case is 2 seconds, needed for FAT. */
static int const delaytab[] = {1, 1000, 20000, 1000000 };
static int const delaytab[] = {1, 1000, 1000000, 15250000, 1000000000 };
int fd = creat (BASE "tmp", 0600);
int i;
int delay = 2000000;
int delay = 2000000000;
struct stat st;
ASSERT (0 <= fd);
get_mtime (fd, &st, 0);
get_stat (fd, &st, 0);
for (i = 0; i < sizeof delaytab / sizeof delaytab[0]; i++)
if (nap_works (fd, delaytab[i], &st))
{
delay = delaytab[i];
break;
}
{
int d = nap_works (fd, delaytab[i], &st);
if (d != 0)
{
delay = d;
break;
}
}
ASSERT (close (fd) == 0);
ASSERT (unlink (BASE "tmp") == 0);
return delay;
@@ -90,14 +115,24 @@ guess_delay (void)
/* Sleep long enough to notice a timestamp difference on the file
system in the current directory. Assumes that BASE is defined,
and requires that the test module depends on usleep. */
and requires that the test module depends on nanosleep. */
static void
nap (void)
{
static int delay;
if (!delay)
delay = guess_delay ();
usleep (delay);
static struct timespec delay;
if (!delay.tv_sec && !delay.tv_nsec)
{
int d = guess_delay ();
/* Multiply by 1.125 (rounding up), to avoid problems if the
file system's clock is a bit slower than nanosleep's.
Ceiling it at INT_MAX, though. */
int delta = (d >> 3) + ((d & 7) != 0);
d = delta < INT_MAX - d ? d + delta : INT_MAX;
delay.tv_sec = d / 1000000000;
delay.tv_nsec = d % 1000000000;
}
ASSERT (nanosleep (&delay, 0) == 0);
}
#endif /* GLTEST_NAP_H */

45
tests/test-stat-time.c
View File

@@ -27,6 +27,9 @@
#include "macros.h"
#define BASE "test-stat-time.t"
#include "nap.h"
enum { NFILES = 4 };
static int
@@ -79,48 +82,6 @@ do_stat (const char *filename, struct stat *p)
ASSERT (stat (filename, p) == 0);
}
/* Sleep long enough to notice a timestamp difference on the file
system in the current directory. */
static void
nap (void)
{
static long delay;
if (!delay)
{
/* Initialize only once, by sleeping for 20 milliseconds (needed
since xfs has a quantization of about 10 milliseconds, even
though it has a granularity of 1 nanosecond, and since NTFS
has a default quantization of 15.25 milliseconds, even though
it has a granularity of 100 nanoseconds). If the seconds
differ, repeat the test one more time (in case we crossed a
quantization boundary on a file system with 1 second
resolution). If we can't observe a difference in only the
nanoseconds, then fall back to 1 second if the time is odd,
and 2 seconds (needed for FAT) if time is even. */
struct stat st1;
struct stat st2;
ASSERT (stat ("t-stt-stamp1", &st1) == 0);
ASSERT (force_unlink ("t-stt-stamp1") == 0);
delay = 20000;
usleep (delay);
create_file ("t-stt-stamp1");
ASSERT (stat ("t-stt-stamp1", &st2) == 0);
if (st1.st_mtime != st2.st_mtime)
{
/* Seconds differ, give it one more shot. */
st1 = st2;
ASSERT (force_unlink ("t-stt-stamp1") == 0);
usleep (delay);
create_file ("t-stt-stamp1");
ASSERT (stat ("t-stt-stamp1", &st2) == 0);
}
if (! (st1.st_mtime == st2.st_mtime
&& get_stat_mtime_ns (&st1) < get_stat_mtime_ns (&st2)))
delay = (st1.st_mtime & 1) ? 1000000 : 2000000;
}
usleep (delay);
}
static void
prepare_test (struct stat *statinfo, struct timespec *modtimes)
{