When we generate our own semaphore name (internally) when using

Posix semaphores, initially try a name more unique (which unfortunately
may also be larger than the least-common-denominator in names).
If that fails, however, we gracefully use the old naming mechanism.
PR:
Obtained from:
Submitted by:
Reviewed by:


git-svn-id: http://svn.apache.org/repos/asf/apr/apr/trunk@64371 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 23 insertions, 7 deletions

diff --git a/locks/unix/proc_mutex.c b/locks/unix/proc_mutex.c
index 67656d867..2d3eebf2d 100644
--- a/locks/unix/proc_mutex.c
+++ b/locks/unix/proc_mutex.c
@@ -91,9 +91,10 @@ static apr_status_t proc_mutex_posix_create(apr_proc_mutex_t *new_mutex,
 {
     sem_t *psem;
     apr_status_t stat;
-    char semname[14];
+    char semname[31];
     apr_time_t now;
-    unsigned long epoch;
+    unsigned long sec;
+    unsigned long usec;
     
     new_mutex->interproc = apr_palloc(new_mutex->pool,
                                       sizeof(*new_mutex->interproc));
@@ -104,20 +105,34 @@ static apr_status_t proc_mutex_posix_create(apr_proc_mutex_t *new_mutex,
      *   - be at most 14 chars
      *   - be unique and not match anything on the filesystem
      *
-     * Because of this, we ignore fname and craft our own.
+     * Because of this, we ignore fname, and try our
+     * own naming system. We tuck the name away, since it might
+     * be useful for debugging. to  make this as robust as possible,
+     * we initially try something larger (and hopefully more unique)
+     * and gracefully fail down to the LCD above.
+     *
+     * NOTE: Darwin (Mac OS X) seems to be the most restrictive
+     * implementation. Versions previous to Darwin 6.2 had the 14
+     * char limit, but later rev's allow up to 31 characters.
      *
      * FIXME: There is a small window of opportunity where
      * instead of getting a new semaphore descriptor, we get
      * a previously obtained one. This can happen if the requests
-     * are made at the "same time" (within a second, due to the
-     * apr_time_now() call) and in the small span of time between
+     * are made at the "same time" and in the small span of time between
      * the sem_open and the sem_unlink. Use of O_EXCL does not
      * help here however...
+     *
      */
     now = apr_time_now();
-    epoch = apr_time_sec(now);
-    apr_snprintf(semname, sizeof(semname), "/ApR.%lx", epoch);
+    sec = apr_time_sec(now);
+    usec = apr_time_usec(now);
+    apr_snprintf(semname, sizeof(semname), "/ApR.%lxZ%lx", sec, usec);
     psem = sem_open((const char *) semname, O_CREAT, 0644, 1);
+    if ((psem == (sem_t *)SEM_FAILED) && (errno == ENAMETOOLONG)) {
+        /* Oh well, good try */
+        semname[13] = '\0';
+        psem = sem_open((const char *) semname, O_CREAT, 0644, 1);
+    }
 
     if (psem == (sem_t *)SEM_FAILED) {
         stat = errno;
@@ -127,6 +142,7 @@ static apr_status_t proc_mutex_posix_create(apr_proc_mutex_t *new_mutex,
     /* Ahhh. The joys of Posix sems. Predelete it... */
     sem_unlink((const char *) semname);
     new_mutex->interproc->filedes = (int)psem;	/* Ugg */
+    new_mutex->fname = apr_pstrdup(new_mutex->pool, semname);
     apr_pool_cleanup_register(new_mutex->pool, (void *)new_mutex,
                               apr_proc_mutex_cleanup, 
                               apr_pool_cleanup_null);