LU-11089 obdclass: remove locking from lu_context_exit()

[fs/lustre-release.git] / lustre / obdclass / lu_object.c

diff --git a/lustre/obdclass/lu_object.c b/lustre/obdclass/lu_object.c
index 63729fe..9f62693 100644 (file)
--- a/lustre/obdclass/lu_object.c
+++ b/lustre/obdclass/lu_object.c
@@ -42,6 +42,12 @@
 
 #include <linux/module.h>
 #include <linux/list.h>
+#ifdef HAVE_PROCESSOR_H
+#include <linux/processor.h>
+#else
+#include <libcfs/linux/processor.h>
+#endif
+
 #include <libcfs/libcfs.h>
 #include <libcfs/libcfs_hash.h> /* hash_long() */
 #include <libcfs/linux/linux-mem.h>
@@ -1560,8 +1566,11 @@ void lu_context_key_quiesce(struct lu_context_key *key)
                up_write(&lu_key_initing);
 
                write_lock(&lu_keys_guard);
-               list_for_each_entry(ctx, &lu_context_remembered, lc_remember)
+               list_for_each_entry(ctx, &lu_context_remembered, lc_remember) {
+                       spin_until_cond(READ_ONCE(ctx->lc_state) != LCS_LEAVING);
                        key_fini(ctx, key->lct_index);
+               }
+
                write_unlock(&lu_keys_guard);
        }
 }
@@ -1721,28 +1730,35 @@ void lu_context_exit(struct lu_context *ctx)
 {
        unsigned int i;
 
-        LINVRNT(ctx->lc_state == LCS_ENTERED);
-        ctx->lc_state = LCS_LEFT;
-        if (ctx->lc_tags & LCT_HAS_EXIT && ctx->lc_value != NULL) {
-               /* could race with key quiescency */
-               if (ctx->lc_tags & LCT_REMEMBER)
-                       read_lock(&lu_keys_guard);
-
+       LINVRNT(ctx->lc_state == LCS_ENTERED);
+       /*
+        * Disable preempt to ensure we get a warning if
+        * any lct_exit ever tries to sleep.  That would hurt
+        * lu_context_key_quiesce() which spins waiting for us.
+        * This also ensure we aren't preempted while the state
+        * is LCS_LEAVING, as that too would cause problems for
+        * lu_context_key_quiesce().
+        */
+       preempt_disable();
+       /*
+        * Ensure lu_context_key_quiesce() sees LCS_LEAVING
+        * or we see LCT_QUIESCENT
+        */
+       smp_store_mb(ctx->lc_state, LCS_LEAVING);
+       if (ctx->lc_tags & LCT_HAS_EXIT && ctx->lc_value) {
                 for (i = 0; i < ARRAY_SIZE(lu_keys); ++i) {
-                       if (ctx->lc_value[i] != NULL) {
-                               struct lu_context_key *key;
-
-                               key = lu_keys[i];
-                               LASSERT(key != NULL);
-                               if (key->lct_exit != NULL)
-                                       key->lct_exit(ctx,
-                                                     key, ctx->lc_value[i]);
-                       }
-                }
+                       struct lu_context_key *key;
 
-               if (ctx->lc_tags & LCT_REMEMBER)
-                       read_unlock(&lu_keys_guard);
+                       key = lu_keys[i];
+                       if (ctx->lc_value[i] &&
+                           !(key->lct_tags & LCT_QUIESCENT) &&
+                           key->lct_exit)
+                               key->lct_exit(ctx, key, ctx->lc_value[i]);
+               }
         }
+
+       smp_store_release(&ctx->lc_state, LCS_LEFT);
+       preempt_enable();
 }
 EXPORT_SYMBOL(lu_context_exit);