Update.
2003-05-17 Ulrich Drepper <drepper@redhat.com> * sem_open.c: Fix one endless loop. Implement correct semantics wrt opening the same semaphore more then once. * sem_close.c: Adjust for sem_open change. * semaphoreP.h: Include <semaphore.h>. Define struct inuse_sem. Declare __sem_mappings, __sem_mappings_lock, __sem_search. * Makefile (tests): Add tst-sem7. * tst-sem7.c: New file.
This commit is contained in:
Ulrich Drepper
parent
68a396e83a
commit
fddfebbd10
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@ -1,3 +1,13 @@
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2003-05-17 Ulrich Drepper <drepper@redhat.com>
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* sem_open.c: Fix one endless loop. Implement correct semantics
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wrt opening the same semaphore more then once.
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* sem_close.c: Adjust for sem_open change.
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* semaphoreP.h: Include <semaphore.h>. Define struct inuse_sem.
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Declare __sem_mappings, __sem_mappings_lock, __sem_search.
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* Makefile (tests): Add tst-sem7.
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* tst-sem7.c: New file.
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2003-05-16 Roland McGrath <roland@redhat.com>
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* sysdeps/unix/sysv/linux/register-atfork.c (libc_freeres_fn): Fix
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@ -149,7 +149,7 @@ tests = tst-attr1 tst-attr2 \
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tst-rwlock11 \
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tst-once1 tst-once2 tst-once3 tst-once4 \
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tst-key1 tst-key2 tst-key3 tst-key4 \
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tst-sem1 tst-sem2 tst-sem3 tst-sem4 tst-sem5 tst-sem6 \
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tst-sem1 tst-sem2 tst-sem3 tst-sem4 tst-sem5 tst-sem6 tst-sem7 \
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tst-barrier1 tst-barrier2 tst-barrier3 \
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tst-align \
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tst-basic1 tst-basic2 tst-basic3 tst-basic4 tst-basic5 tst-basic6 \
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175
nptl/sem_open.c
175
nptl/sem_open.c
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@ -22,6 +22,7 @@
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#include <mntent.h>
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#include <paths.h>
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#include <pthread.h>
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#include <search.h>
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#include <semaphore.h>
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#include <stdarg.h>
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#include <stdio.h>
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@ -122,11 +123,105 @@ __where_is_shmfs (void)
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}
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/* Comparison function for search of existing mapping. */
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int
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attribute_hidden
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__sem_search (const void *a, const void *b)
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{
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const struct inuse_sem *as = (const struct inuse_sem *) a;
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const struct inuse_sem *bs = (const struct inuse_sem *) b;
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if (as->ino != bs->ino)
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/* Cannot return the difference the type is larger than int. */
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return as->ino < bs->ino ? -1 : (as->ino == bs->ino ? 0 : 1);
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if (as->dev != bs->dev)
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/* Cannot return the difference the type is larger than int. */
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return as->dev < bs->dev ? -1 : (as->dev == bs->dev ? 0 : 1);
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return strcmp (as->name, bs->name);
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}
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/* The search tree for existing mappings. */
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void *__sem_mappings attribute_hidden;
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/* Lock to protect the search tree. */
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lll_lock_t __sem_mappings_lock = LLL_LOCK_INITIALIZER;
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/* Search for existing mapping and if possible add the one provided. */
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static sem_t *
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check_add_mapping (const char *name, size_t namelen, int fd, sem_t *existing)
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{
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sem_t *result = SEM_FAILED;
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/* Get the information about the file. */
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struct stat64 st;
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if (__fxstat64 (_STAT_VER, fd, &st) == 0)
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{
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/* Get the lock. */
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lll_lock (__sem_mappings_lock);
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/* Search for an existing mapping given the information we have. */
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struct inuse_sem *fake;
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fake = (struct inuse_sem *) alloca (sizeof (*fake) + namelen);
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memcpy (fake->name, name, namelen);
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fake->dev = st.st_dev;
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fake->ino = st.st_ino;
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struct inuse_sem **foundp = tfind (fake, &__sem_mappings, __sem_search);
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if (foundp != NULL)
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{
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/* There is already a mapping. Use it. */
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result = (*foundp)->sem;
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++(*foundp)->refcnt;
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}
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else if (existing != SEM_FAILED)
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{
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/* We haven't found a mapping but the caller has a mapping.
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Install it. */
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struct inuse_sem *newp;
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newp = (struct inuse_sem *) malloc (sizeof (*newp) + namelen);
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if (newp != NULL)
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{
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newp->dev = st.st_dev;
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newp->ino = st.st_ino;
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newp->refcnt = 1;
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newp->sem = existing;
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memcpy (newp->name, name, namelen);
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/* Insert the new value. */
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if (tsearch (newp, &__sem_mappings, __sem_search) != NULL)
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/* Successful. */
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result = existing;
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else
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/* Something went wrong while inserting the new
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value. We fail completely. */
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free (newp);
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}
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}
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/* Release the lock. */
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lll_unlock (__sem_mappings_lock);
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}
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if (result != existing && existing != SEM_FAILED)
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{
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/* Do not disturb errno. */
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INTERNAL_SYSCALL_DECL (err);
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INTERNAL_SYSCALL (munmap, err, 2, existing, sizeof (sem_t));
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}
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return result;
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}
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sem_t *
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sem_open (const char *name, int oflag, ...)
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{
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char *finalname;
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size_t namelen;
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sem_t *result = SEM_FAILED;
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int fd;
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@ -150,12 +245,12 @@ sem_open (const char *name, int oflag, ...)
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__set_errno (EINVAL);
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return SEM_FAILED;
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}
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namelen = strlen (name);
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size_t namelen = strlen (name) + 1;
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/* Create the name of the final file. */
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finalname = (char *) alloca (mountpoint.dirlen + namelen + 1);
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finalname = (char *) alloca (mountpoint.dirlen + namelen);
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__mempcpy (__mempcpy (finalname, mountpoint.dir, mountpoint.dirlen),
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name, namelen + 1);
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name, namelen);
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/* If the semaphore object has to exist simply open it. */
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if ((oflag & O_CREAT) == 0 || (oflag & O_EXCL) == 0)
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@ -167,15 +262,22 @@ sem_open (const char *name, int oflag, ...)
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if (fd == -1)
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{
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/* If we are supposed to create the file try this next. */
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if ((oflag & O_CREAT) != 0)
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if ((oflag & O_CREAT) != 0 && errno == ENOENT)
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goto try_create;
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/* Return. errno is already set. */
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}
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else
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/* Map the sem_t structure from the file. */
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result = (sem_t *) mmap (NULL, sizeof (sem_t), PROT_READ | PROT_WRITE,
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MAP_SHARED, fd, 0);
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{
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/* Check whether we already have this semaphore mapped. */
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result = check_add_mapping (name, namelen, fd, SEM_FAILED);
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/* Map the sem_t structure from the file. */
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if (result == SEM_FAILED)
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result = (sem_t *) mmap (NULL, sizeof (sem_t),
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PROT_READ | PROT_WRITE, MAP_SHARED,
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fd, 0);
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}
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}
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else
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{
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@ -200,14 +302,6 @@ sem_open (const char *name, int oflag, ...)
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return SEM_FAILED;
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}
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tmpfname = (char *) alloca (mountpoint.dirlen + 6 + 1);
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strcpy (__mempcpy (tmpfname, mountpoint.dir, mountpoint.dirlen),
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"XXXXXX");
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fd = mkstemp (tmpfname);
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if (fd == -1)
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return SEM_FAILED;
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/* Create the initial file content. */
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sem_t initsem;
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@ -218,10 +312,44 @@ sem_open (const char *name, int oflag, ...)
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memset ((char *) &initsem + sizeof (struct sem), '\0',
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sizeof (sem_t) - sizeof (struct sem));
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tmpfname = (char *) alloca (mountpoint.dirlen + 6 + 1);
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char *xxxxxx = __mempcpy (tmpfname, mountpoint.dir, mountpoint.dirlen);
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int retries = 0;
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#define NRETRIES 50
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while (1)
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{
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/* Add the suffix for mktemp. */
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strcpy (xxxxxx, "XXXXXX");
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/* We really want to use mktemp here. We cannot use mkstemp
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since the file must be opened with a specific mode. The
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mode cannot later be set since then we cannot apply the
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file create mask. */
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if (mktemp (tmpfname) == NULL)
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return SEM_FAILED;
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/* Open the file. Make sure we do not overwrite anything. */
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fd = __libc_open (tmpfname, O_RDWR | O_CREAT | O_EXCL, mode);
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if (fd == -1)
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{
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if (errno == EEXIST)
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{
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if (++retries < NRETRIES)
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continue;
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__set_errno (EAGAIN);
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}
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return SEM_FAILED;
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}
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/* We got a file. */
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break;
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}
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if (TEMP_FAILURE_RETRY (__libc_write (fd, &initsem, sizeof (sem_t)))
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== sizeof (sem_t)
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/* Adjust the permission. */
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&& fchmod (fd, mode) == 0
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/* Map the sem_t structure from the file. */
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&& (result = (sem_t *) mmap (NULL, sizeof (sem_t),
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PROT_READ | PROT_WRITE, MAP_SHARED,
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@ -249,6 +377,11 @@ sem_open (const char *name, int oflag, ...)
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goto try_again;
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}
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}
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else
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/* Insert the mapping into the search tree. This also
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determines whether another thread sneaked by and already
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added such a mapping despite the fact that we created it. */
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result = check_add_mapping (name, namelen, fd, result);
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}
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/* Now remove the temporary name. This should never fail. If
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@ -262,7 +395,11 @@ sem_open (const char *name, int oflag, ...)
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/* We don't need the file descriptor anymore. */
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if (fd != -1)
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(void) __libc_close (fd);
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{
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/* Do not disturb errno. */
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INTERNAL_SYSCALL_DECL (err);
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INTERNAL_SYSCALL (close, err, 1, fd);
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}
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return result;
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}
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@ -1,4 +1,4 @@
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/* Copyright (C) 2002 Free Software Foundation, Inc.
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/* Copyright (C) 2002, 2003 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
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@ -17,8 +17,10 @@
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Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA. */
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#include <semaphore.h>
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#include "pthreadP.h"
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/* Mount point of the shared memory filesystem. */
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struct mountpoint_info
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{
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@ -26,16 +28,35 @@ struct mountpoint_info
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size_t dirlen;
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};
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/* Keeping track of currently used mappings. */
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struct inuse_sem
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{
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dev_t dev;
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ino_t ino;
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int refcnt;
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sem_t *sem;
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char name[0];
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};
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/* Variables used in multiple interfaces. */
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extern struct mountpoint_info mountpoint attribute_hidden;
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extern pthread_once_t __namedsem_once attribute_hidden;
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/* The search tree for existing mappings. */
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extern void *__sem_mappings attribute_hidden;
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/* Lock to protect the search tree. */
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extern lll_lock_t __sem_mappings_lock;
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/* Initializer for mountpoint. */
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extern void __where_is_shmfs (void) attribute_hidden;
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/* Comparison function for search in tree with existing mappings. */
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extern int __sem_search (const void *a, const void *b) attribute_hidden;
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/* Prototypes of functions with multiple interfaces. */
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extern int __new_sem_init (sem_t *sem, int pshared, unsigned int value);
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@ -0,0 +1,109 @@
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/* Copyright (C) 2003 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@redhat.com>, 2003.
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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, write to the Free
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Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA. */
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#include <errno.h>
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#include <fcntl.h>
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#include <semaphore.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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static void
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remove_sem (int status, void *arg)
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{
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sem_unlink (arg);
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}
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int
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main (void)
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{
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sem_t *s;
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sem_t *s2;
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sem_t *s3;
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s = sem_open ("/glibc-tst-sem7", O_CREAT, 0600, 1);
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if (s == SEM_FAILED)
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{
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if (errno == ENOSYS)
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{
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puts ("sem_open not supported. Oh well.");
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return 0;
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}
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/* Maybe the shm filesystem has strict permissions. */
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if (errno == EACCES)
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{
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puts ("sem_open not allowed. Oh well.");
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return 0;
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}
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printf ("sem_open: %m\n");
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return 1;
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}
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on_exit (remove_sem, (void *) "/glibc-tst-sem7");
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/* We have the semaphore object. Now try again. We should get the
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same address. */
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s2 = sem_open ("/glibc-tst-sem7", O_CREAT, 0600, 1);
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if (s2 == SEM_FAILED)
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{
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puts ("2nd sem_open failed");
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return 1;
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}
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if (s != s2)
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{
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puts ("2nd sem_open didn't return the same address");
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return 1;
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}
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/* And again, this time without O_CREAT. */
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s3 = sem_open ("/glibc-tst-sem7", 0);
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if (s3 == SEM_FAILED)
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{
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puts ("3rd sem_open failed");
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return 1;
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}
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if (s != s3)
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{
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puts ("3rd sem_open didn't return the same address");
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return 1;
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}
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/* Now close the handle. Three times. */
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if (sem_close (s2) != 0)
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{
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puts ("1st sem_close failed");
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return 1;
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}
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if (sem_close (s) != 0)
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{
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puts ("2nd sem_close failed");
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return 1;
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}
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if (sem_close (s3) != 0)
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{
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puts ("3rd sem_close failed");
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return 1;
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}
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return 0;
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}
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