Be a bit more clear about the FIXME statement and the exact

window we're concerned about.

When oh when will we depreciate the old locking stuff :)
PR:
Obtained from:
Submitted by:
Reviewed by:


git-svn-id: http://svn.apache.org/repos/asf/apr/apr/trunk@63225 13f79535-47bb-0310-9956-ffa450edef68

2 files changed, 14 insertions, 6 deletions

diff --git a/locks/unix/crossproc.c b/locks/unix/crossproc.c
index e7988cd4a..78af3f1c5 100644
--- a/locks/unix/crossproc.c
+++ b/locks/unix/crossproc.c
@@ -98,9 +98,13 @@ static apr_status_t posix_create(apr_lock_t *new, const char *fname)
      *
      * Because of this, we ignore fname and craft our own.
      *
-     * FIXME: if we try to create another semaphore within a second
-     * of creating this on, we won't get a new one but another
-     * reference to this one.
+     * 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
+     * the sem_open and the sem_unlink. Use of O_EXCL does not
+     * help here however...
      */
     epoch = apr_time_now() / APR_USEC_PER_SEC;
     apr_snprintf(semname, sizeof(semname), "/ApR.%lx", epoch);
diff --git a/locks/unix/proc_mutex.c b/locks/unix/proc_mutex.c
index ae7000e3c..e1a548598 100644
--- a/locks/unix/proc_mutex.c
+++ b/locks/unix/proc_mutex.c
@@ -99,9 +99,13 @@ static apr_status_t proc_mutex_posix_create(apr_proc_mutex_t *new_mutex,
      *
      * Because of this, we ignore fname and craft our own.
      *
-     * FIXME: if we try to create another semaphore within a second
-     * of creating this on, we won't get a new one but another
-     * reference to this one.
+     * 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
+     * the sem_open and the sem_unlink. Use of O_EXCL does not
+     * help here however...
      */
     epoch = apr_time_now() / APR_USEC_PER_SEC;
     apr_snprintf(semname, sizeof(semname), "/ApR.%lx", epoch);