xnu-517.3.7.tar.gz

[apple/xnu.git] / bsd / vm / vm_unix.c

diff --git a/bsd/vm/vm_unix.c b/bsd/vm/vm_unix.c
index be634ec2bdc0f6283bf5d14fa9fb5058e7aa8381..f84e8b4c54e02cdeac902636688a0fd48a829fa4 100644 (file)
--- a/bsd/vm/vm_unix.c
+++ b/bsd/vm/vm_unix.c
@@ -955,48 +955,92 @@ restart:
        }
 
        lru = global_user_profile_cache.age;
+       *profile = NULL;
        for(i = 0; i<global_user_profile_cache.max_ele; i++) {
+               /* Skip entry if it is in the process of being reused */
+               if(global_user_profile_cache.profiles[i].data_vp ==
+                                               (struct vnode *)0xFFFFFFFF)
+                       continue;
+               /* Otherwise grab the first empty entry */
                if(global_user_profile_cache.profiles[i].data_vp == NULL) {
                        *profile = &global_user_profile_cache.profiles[i];
                        (*profile)->age = global_user_profile_cache.age;
-                       global_user_profile_cache.age+=1;
                        break;
                }
+               /* Otherwise grab the oldest entry */
                if(global_user_profile_cache.profiles[i].age < lru) {
                        lru = global_user_profile_cache.profiles[i].age;
                        *profile = &global_user_profile_cache.profiles[i];
                }
        }
 
+       /* Did we set it? */
+       if (*profile == NULL) {
+               /*
+                * No entries are available; this can only happen if all
+                * of them are currently in the process of being reused;
+                * if this happens, we sleep on the address of the first
+                * element, and restart.  This is less than ideal, but we
+                * know it will work because we know that there will be a
+                * wakeup on any entry currently in the process of being
+                * reused.
+                *
+                * XXX Reccomend a two handed clock and more than 3 total
+                * XXX cache entries at some point in the future.
+                */
+                       /*
+                       * drop funnel and wait 
+                       */
+               (void)tsleep((void *)
+                &global_user_profile_cache.profiles[0],
+                       PRIBIO, "app_profile", 0);
+               goto restart;
+       }
+
+       /*
+        * If it's currently busy, we've picked the one at the end of the
+        * LRU list, but it's currently being actively used.  We sleep on
+        * its address and restart.
+        */
        if ((*profile)->busy) {
                        /*
                        * drop funnel and wait 
                        */
                (void)tsleep((void *)
-                       &(global_user_profile_cache), 
+                       *profile, 
                        PRIBIO, "app_profile", 0);
                goto restart;
        }
        (*profile)->busy = 1;
        (*profile)->user = user;
 
-       if((*profile)->data_vp != NULL) {
+       /*
+        * put dummy value in for now to get competing request to wait
+        * above until we are finished
+        *
+        * Save the data_vp before setting it, so we can set it before
+        * we kmem_free() or vrele().  If we don't do this, then we
+        * have a potential funnel race condition we have to deal with.
+        */
+       data_vp = (*profile)->data_vp;
+       (*profile)->data_vp = (struct vnode *)0xFFFFFFFF;
+
+       /*
+        * Age the cache here in all cases; this guarantees that we won't
+        * be reusing only one entry over and over, once the system reaches
+        * steady-state.
+        */
+       global_user_profile_cache.age+=1;
+
+       if(data_vp != NULL) {
                kmem_free(kernel_map, 
                                (*profile)->buf_ptr, 4 * PAGE_SIZE);
                if ((*profile)->names_vp) {
                        vrele((*profile)->names_vp);
                        (*profile)->names_vp = NULL;
                }
-               if ((*profile)->data_vp) {
-                       vrele((*profile)->data_vp);
-                       (*profile)->data_vp = NULL;
-               }
+               vrele(data_vp);
        }
-
-       /* put dummy value in for now to get */
-       /* competing request to wait above   */
-       /* until we are finished */
-       (*profile)->data_vp = (struct vnode *)0xFFFFFFFF;
        
        /* Try to open the appropriate users profile files */
        /* If neither file is present, try to create them  */
@@ -1004,7 +1048,6 @@ restart:
        /* If the files do exist, check them for the app_file */
        /* requested and read it in if present */
 
-
        ret = kmem_alloc(kernel_map,
                (vm_offset_t *)&profile_data_string, PATH_MAX);
 
@@ -1385,7 +1428,7 @@ bsd_search_page_cache_data_base(
                resid_off = 0;
                while(size) {
                        error = vn_rdwr(UIO_READ, vp, 
-                               (caddr_t)(local_buf + resid_off),
+                               CAST_DOWN(caddr_t, (local_buf + resid_off)),
                                size, file_off + resid_off, UIO_SYSSPACE, 
                                IO_NODELOCKED, p->p_ucred, &resid, p);
                        if((error) || (size == resid)) {