Remove unnecessary locking when reading iconv configuration [BZ #22062]
In iconv/gconv_conf.c, __gconv_get_path unnecessarily obtains a lock when populating the array pointed to by __gconv_path_elem. The locking is not necessary because all calls to __gconv_read_conf (which in turn calls __gconv_get_path) are serialized using __libc_once. This patch: - removes all locking in __gconv_get_path; - replaces all explicitly serialized __gconv_read_conf calls with calls to __gconv_load_conf, a new wrapper that is serialized internally; - adds a new test, iconv/tst-iconv_mt.c, to exercise iconv initialization, usage, and cleanup in a multi-threaded program; - indents __gconv_get_path correctly, removing tab characters (which makes the patch look a little bigger than it really is). After removing the unnecessary locking, it was confirmed that the test case fails if the relevant __libc_once is removed. Additionally, four localedata and iconvdata tests also fail. This gives confidence that the testsuite sufficiently guards against some regressions relating to multi-threading with iconv. Tested on x86_64 and i686.
This commit is contained in:
Arjun Shankar
parent
729f34028a
commit
c5288d378a
16
ChangeLog
16
ChangeLog
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@ -1,3 +1,19 @@
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2018-10-17 Arjun Shankar <arjun@redhat.com>
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[BZ #22062]
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* iconv/gconv_conf.c (__gconv_get_path): Remove locking and fix
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indentation.
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* (__gconv_read_conf): Mark function static.
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* (once): New static variable.
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* (__gconv_load_conf): New function.
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* iconv/gconv_int.h (__gconv_load_conf): Likewise.
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* iconv/gconv_db.c (once): Remove static variable.
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* (__gconv_compare_alias): Use __gconv_load_conf instead of
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__gconv_read_conf.
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* (__gconv_find_transform): Likewise.
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* iconv/tst-iconv-mt.c: New test.
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* iconv/Makefile: Add tst-iconv_mt.
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2018-10-17 Joseph Myers <joseph@codesourcery.com>
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* sysdeps/unix/sysv/linux/Makefile (sysdep_headers): Add
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@ -43,7 +43,8 @@ CFLAGS-charmap.c += -DCHARMAP_PATH='"$(i18ndir)/charmaps"' \
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CFLAGS-linereader.c += -DNO_TRANSLITERATION
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CFLAGS-simple-hash.c += -I../locale
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tests = tst-iconv1 tst-iconv2 tst-iconv3 tst-iconv4 tst-iconv5 tst-iconv6
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tests = tst-iconv1 tst-iconv2 tst-iconv3 tst-iconv4 tst-iconv5 tst-iconv6 \
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tst-iconv-mt
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others = iconv_prog iconvconfig
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install-others-programs = $(inst_bindir)/iconv
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@ -67,6 +68,8 @@ endif
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$(objpfx)gconv-modules: test-gconv-modules
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cp $< $@
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$(objpfx)tst-iconv-mt: $(shared-thread-library)
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ifeq (yes,$(build-shared))
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tests += tst-gconv-init-failure
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modules-names += tst-gconv-init-failure-mod
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@ -426,119 +426,115 @@ read_conf_file (const char *filename, const char *directory, size_t dir_len,
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}
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/* Determine the directories we are looking for data in. */
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/* Determine the directories we are looking for data in. This function should
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only be called from __gconv_read_conf. */
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static void
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__gconv_get_path (void)
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{
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struct path_elem *result;
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__libc_lock_define_initialized (static, lock);
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__libc_lock_lock (lock);
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/* This function is only ever called when __gconv_path_elem is NULL. */
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result = __gconv_path_elem;
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assert (result == NULL);
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/* Make sure there wasn't a second thread doing it already. */
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result = (struct path_elem *) __gconv_path_elem;
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if (result == NULL)
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/* Determine the complete path first. */
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char *gconv_path;
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size_t gconv_path_len;
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char *elem;
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char *oldp;
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char *cp;
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int nelems;
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char *cwd;
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size_t cwdlen;
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if (__gconv_path_envvar == NULL)
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{
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/* Determine the complete path first. */
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char *gconv_path;
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size_t gconv_path_len;
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char *elem;
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char *oldp;
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char *cp;
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int nelems;
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char *cwd;
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size_t cwdlen;
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/* No user-defined path. Make a modifiable copy of the
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default path. */
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gconv_path = strdupa (default_gconv_path);
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gconv_path_len = sizeof (default_gconv_path);
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cwd = NULL;
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cwdlen = 0;
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}
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else
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{
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/* Append the default path to the user-defined path. */
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size_t user_len = strlen (__gconv_path_envvar);
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if (__gconv_path_envvar == NULL)
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{
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/* No user-defined path. Make a modifiable copy of the
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default path. */
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gconv_path = strdupa (default_gconv_path);
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gconv_path_len = sizeof (default_gconv_path);
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cwd = NULL;
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cwdlen = 0;
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}
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else
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{
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/* Append the default path to the user-defined path. */
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size_t user_len = strlen (__gconv_path_envvar);
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gconv_path_len = user_len + 1 + sizeof (default_gconv_path);
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gconv_path = alloca (gconv_path_len);
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__mempcpy (__mempcpy (__mempcpy (gconv_path, __gconv_path_envvar,
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user_len),
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":", 1),
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default_gconv_path, sizeof (default_gconv_path));
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cwd = __getcwd (NULL, 0);
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cwdlen = __glibc_unlikely (cwd == NULL) ? 0 : strlen (cwd);
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}
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assert (default_gconv_path[0] == '/');
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gconv_path_len = user_len + 1 + sizeof (default_gconv_path);
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gconv_path = alloca (gconv_path_len);
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__mempcpy (__mempcpy (__mempcpy (gconv_path, __gconv_path_envvar,
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user_len),
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":", 1),
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default_gconv_path, sizeof (default_gconv_path));
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cwd = __getcwd (NULL, 0);
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cwdlen = __glibc_unlikely (cwd == NULL) ? 0 : strlen (cwd);
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}
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assert (default_gconv_path[0] == '/');
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/* In a first pass we calculate the number of elements. */
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oldp = NULL;
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cp = strchr (gconv_path, ':');
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nelems = 1;
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while (cp != NULL)
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{
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if (cp != oldp + 1)
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++nelems;
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oldp = cp;
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cp = strchr (cp + 1, ':');
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}
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/* Allocate the memory for the result. */
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result = (struct path_elem *) malloc ((nelems + 1)
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* sizeof (struct path_elem)
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+ gconv_path_len + nelems
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+ (nelems - 1) * (cwdlen + 1));
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if (result != NULL)
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{
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char *strspace = (char *) &result[nelems + 1];
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int n = 0;
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/* Separate the individual parts. */
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__gconv_max_path_elem_len = 0;
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elem = __strtok_r (gconv_path, ":", &gconv_path);
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assert (elem != NULL);
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do
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{
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result[n].name = strspace;
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if (elem[0] != '/')
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{
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assert (cwd != NULL);
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strspace = __mempcpy (strspace, cwd, cwdlen);
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*strspace++ = '/';
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}
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strspace = __stpcpy (strspace, elem);
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if (strspace[-1] != '/')
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*strspace++ = '/';
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result[n].len = strspace - result[n].name;
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if (result[n].len > __gconv_max_path_elem_len)
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__gconv_max_path_elem_len = result[n].len;
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*strspace++ = '\0';
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++n;
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}
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while ((elem = __strtok_r (NULL, ":", &gconv_path)) != NULL);
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result[n].name = NULL;
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result[n].len = 0;
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}
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__gconv_path_elem = result ?: (struct path_elem *) &empty_path_elem;
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free (cwd);
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/* In a first pass we calculate the number of elements. */
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oldp = NULL;
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cp = strchr (gconv_path, ':');
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nelems = 1;
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while (cp != NULL)
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{
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if (cp != oldp + 1)
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++nelems;
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oldp = cp;
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cp = strchr (cp + 1, ':');
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}
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__libc_lock_unlock (lock);
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/* Allocate the memory for the result. */
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result = malloc ((nelems + 1)
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* sizeof (struct path_elem)
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+ gconv_path_len + nelems
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+ (nelems - 1) * (cwdlen + 1));
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if (result != NULL)
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{
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char *strspace = (char *) &result[nelems + 1];
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int n = 0;
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/* Separate the individual parts. */
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__gconv_max_path_elem_len = 0;
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elem = __strtok_r (gconv_path, ":", &gconv_path);
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assert (elem != NULL);
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do
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{
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result[n].name = strspace;
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if (elem[0] != '/')
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{
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assert (cwd != NULL);
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strspace = __mempcpy (strspace, cwd, cwdlen);
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*strspace++ = '/';
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}
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strspace = __stpcpy (strspace, elem);
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if (strspace[-1] != '/')
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*strspace++ = '/';
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result[n].len = strspace - result[n].name;
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if (result[n].len > __gconv_max_path_elem_len)
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__gconv_max_path_elem_len = result[n].len;
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*strspace++ = '\0';
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++n;
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}
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while ((elem = __strtok_r (NULL, ":", &gconv_path)) != NULL);
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result[n].name = NULL;
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result[n].len = 0;
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}
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__gconv_path_elem = result ?: (struct path_elem *) &empty_path_elem;
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free (cwd);
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}
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/* Read all configuration files found in the user-specified and the default
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path. */
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void
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attribute_hidden
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path. This function should only be called once during the program's
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lifetime. It disregards locking and synchronization because its only
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caller, __gconv_load_conf, handles this. */
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static void
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__gconv_read_conf (void)
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{
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void *modules = NULL;
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@ -609,6 +605,20 @@ __gconv_read_conf (void)
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}
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/* This "once" variable is used to do a one-time load of the configuration. */
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__libc_once_define (static, once);
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/* Read all configuration files found in the user-specified and the default
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path, but do it only "once" using __gconv_read_conf to do the actual
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work. This is the function that must be called when reading iconv
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configuration. */
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void
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__gconv_load_conf (void)
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{
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__libc_once (once, __gconv_read_conf);
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}
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/* Free all resources if necessary. */
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libc_freeres_fn (free_mem)
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@ -687,10 +687,6 @@ find_derivation (const char *toset, const char *toset_expand,
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}
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/* Control of initialization. */
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__libc_once_define (static, once);
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static const char *
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do_lookup_alias (const char *name)
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{
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@ -709,7 +705,7 @@ __gconv_compare_alias (const char *name1, const char *name2)
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int result;
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/* Ensure that the configuration data is read. */
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__libc_once (once, __gconv_read_conf);
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__gconv_load_conf ();
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if (__gconv_compare_alias_cache (name1, name2, &result) != 0)
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result = strcmp (do_lookup_alias (name1) ?: name1,
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@ -729,7 +725,7 @@ __gconv_find_transform (const char *toset, const char *fromset,
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int result;
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/* Ensure that the configuration data is read. */
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__libc_once (once, __gconv_read_conf);
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__gconv_load_conf ();
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/* Acquire the lock. */
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__libc_lock_lock (__gconv_lock);
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@ -178,8 +178,8 @@ extern int __gconv_compare_alias_cache (const char *name1, const char *name2,
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extern void __gconv_release_step (struct __gconv_step *step)
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attribute_hidden;
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/* Read all the configuration data and cache it. */
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extern void __gconv_read_conf (void) attribute_hidden;
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/* Read all the configuration data and cache it if not done so already. */
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extern void __gconv_load_conf (void) attribute_hidden;
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/* Try to read module cache file. */
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extern int __gconv_load_cache (void) attribute_hidden;
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@ -0,0 +1,142 @@
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/* Test that iconv works in a multi-threaded program.
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Copyright (C) 2017 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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/* This test runs several worker threads that perform the following three
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steps in staggered synchronization with each other:
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1. initialization (iconv_open)
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2. conversion (iconv)
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3. cleanup (iconv_close)
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Having several threads synchronously (using pthread_barrier_*) perform
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these routines exercises iconv code that handles concurrent attempts to
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initialize and/or read global iconv state (namely configuration). */
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#include <iconv.h>
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#include <stdio.h>
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#include <string.h>
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#include <support/support.h>
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#include <support/xthread.h>
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#include <support/check.h>
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#define TCOUNT 16
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_Static_assert (TCOUNT %2 == 0,
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"thread count must be even, since we need two groups.");
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#define CONV_INPUT "Hello, iconv!"
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pthread_barrier_t sync;
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pthread_barrier_t sync_half_pool;
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/* Execute iconv_open, iconv and iconv_close in a synchronized way in
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conjunction with other sibling worker threads. If any step fails, print
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an error to stdout and return NULL to the main thread to indicate the
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error. */
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static void *
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worker (void * arg)
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{
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long int tidx = (long int) arg;
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iconv_t cd;
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char ascii[] = CONV_INPUT;
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char *inbufpos = ascii;
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size_t inbytesleft = sizeof (CONV_INPUT);
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char *utf8 = xcalloc (sizeof (CONV_INPUT), 1);
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char *outbufpos = utf8;
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size_t outbytesleft = sizeof (CONV_INPUT);
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if (tidx < TCOUNT/2)
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/* The first half of the worker thread pool synchronize together here,
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then call iconv_open immediately after. */
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xpthread_barrier_wait (&sync_half_pool);
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else
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/* The second half wait for the first half to finish iconv_open and
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continue to the next barrier (before the call to iconv below). */
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xpthread_barrier_wait (&sync);
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/* The above block of code staggers all subsequent pthread_barrier_wait
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calls in a way that ensures a high chance of encountering these
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combinations of concurrent iconv usage:
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1) concurrent calls to iconv_open,
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2) concurrent calls to iconv_open *and* iconv,
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3) concurrent calls to iconv,
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4) concurrent calls to iconv *and* iconv_close,
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5) concurrent calls to iconv_close. */
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cd = iconv_open ("UTF8", "ASCII");
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TEST_VERIFY_EXIT (cd != (iconv_t) -1);
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xpthread_barrier_wait (&sync);
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TEST_VERIFY_EXIT (iconv (cd, &inbufpos, &inbytesleft, &outbufpos,
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&outbytesleft)
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!= (size_t) -1);
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*outbufpos = '\0';
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xpthread_barrier_wait (&sync);
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TEST_VERIFY_EXIT (iconv_close (cd) == 0);
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/* The next conditional barrier wait is needed because we staggered the
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threads into two groups in the beginning and at this point, the second
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half of worker threads are waiting for the first half to finish
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iconv_close before they can executing the same: */
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if (tidx < TCOUNT/2)
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xpthread_barrier_wait (&sync);
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if (strncmp (utf8, CONV_INPUT, sizeof CONV_INPUT))
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{
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printf ("FAIL: thread %lx: invalid conversion output from iconv\n", tidx);
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pthread_exit ((void *) (long int) 1);
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}
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pthread_exit (NULL);
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}
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static int
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do_test (void)
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{
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pthread_t thread[TCOUNT];
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void * worker_output;
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int i;
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xpthread_barrier_init (&sync, NULL, TCOUNT);
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xpthread_barrier_init (&sync_half_pool, NULL, TCOUNT/2);
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for (i = 0; i < TCOUNT; i++)
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thread[i] = xpthread_create (NULL, worker, (void *) (long int) i);
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for (i = 0; i < TCOUNT; i++)
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{
|
||||
worker_output = xpthread_join (thread[i]);
|
||||
TEST_VERIFY_EXIT (worker_output == NULL);
|
||||
}
|
||||
|
||||
xpthread_barrier_destroy (&sync);
|
||||
xpthread_barrier_destroy (&sync_half_pool);
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
#include <support/test-driver.c>
|
||||
Loading…
Reference in New Issue