jlaitine commented on code in PR #8026:
URL: https://github.com/apache/nuttx/pull/8026#discussion_r1065468467
##########
mm/shm/shmdt.c:
##########
@@ -178,4 +164,55 @@ int shmdt(FAR const void *shmaddr)
return ERROR;
}
+int shmdt(FAR const void *shmaddr)
+{
+ FAR struct tcb_s *tcb;
+ FAR struct mm_map_entry_s *entry;
+ FAR struct task_group_s *group;
+ int shmid;
+ int ret;
+
+ /* Get the TCB and group containing our virtual memory allocator */
+
+ tcb = nxsched_self();
+ DEBUGASSERT(tcb && tcb->group);
+ group = tcb->group;
+
+ /* Get exclusive access to process' mm_map */
+
+ ret = mm_map_lock();
+ if (ret == OK)
+ {
+ /* Perform the reverse lookup to get the shmid corresponding to this
+ * shmaddr. The mapping is matched with just shmaddr == map->vaddr.
+ */
+
+ entry = mm_map_find(shmaddr, 1);
+ if (!entry || entry->vaddr != shmaddr)
+ {
+ ret = -EINVAL;
+ shmerr("ERROR: No region matching this virtual address: %p\n",
+ shmaddr);
+
+ mm_map_unlock();
+ return -EINVAL;
+ }
+
+ shmid = entry->priv.i;
+
+ /* Indicate that there is no longer any mapping for this region. */
+
+ if (mm_map_remove(get_group_mm(group), entry) < 0)
+ {
+ shmerr("ERROR: mm_map_remove() failed\n");
+ }
+
+ mm_map_unlock();
+
+ ret = shmdt_priv(tcb->group, shmaddr, shmid);
Review Comment:
There are two ways to unmap the shm region by the user. sysv "shmdt" call
(see "man shmdt"), and "unmap" call.
- sysv "shmdt" call is always done during normal user process execution
- unmap call could be done during normal process execution (but normally
you'd use the shmdt if using this interface)
- unmap call can be done during proceess exit, if user has left the memory
unmapped, or process dies unexpectedly
shmdt_priv is the common function which does the actual work for all cases.
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