[src/trunk]: src/sys/external/bsd/drm2/linux Tweak slightly sketchy logic in ...

[riastradh <riastradh%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/e42752fd0b92
branches:  trunk
changeset: 825631:e42752fd0b92
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Wed Jul 26 03:40:39 2017 +0000

description:
Tweak slightly sketchy logic in linux_idr.

1. idr_preload can fail if you don't set __GFP_WAIT.
2. If idr_preload fails, it is wrong for idr_alloc to assert.
3. There is no way for idr_alloc to know what flags idr_preload got.

Probably won't *fix* any bugs, but if there is a bug with a missing
__GFP_WAIT, then we will learn about a trifle sooner.

diffstat:

 sys/external/bsd/drm2/linux/linux_idr.c |  11 +++++++----
 1 files changed, 7 insertions(+), 4 deletions(-)

diffs (39 lines):

diff -r aaa44887bb2c -r e42752fd0b92 sys/external/bsd/drm2/linux/linux_idr.c
--- a/sys/external/bsd/drm2/linux/linux_idr.c   Wed Jul 26 01:33:35 2017 +0000
+++ b/sys/external/bsd/drm2/linux/linux_idr.c   Wed Jul 26 03:40:39 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: linux_idr.c,v 1.5 2015/01/01 01:15:43 mrg Exp $        */
+/*     $NetBSD: linux_idr.c,v 1.6 2017/07/26 03:40:39 riastradh Exp $  */
 
 /*-
  * Copyright (c) 2013 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: linux_idr.c,v 1.5 2015/01/01 01:15:43 mrg Exp $");
+__KERNEL_RCSID(0, "$NetBSD: linux_idr.c,v 1.6 2017/07/26 03:40:39 riastradh Exp $");
 
 #include <sys/param.h>
 #include <sys/atomic.h>
@@ -191,6 +191,7 @@
                ASSERT_SLEEPABLE();
 
        node = kmalloc(sizeof(*node), gfp);
+       KASSERT(node != NULL || !ISSET(gfp, __GFP_WAIT));
        if (node == NULL)
                return;
 
@@ -216,8 +217,10 @@
 
        /* Grab a node allocated by idr_preload.  */
        mutex_spin_enter(&idr_cache.lock);
-       KASSERTMSG(!SIMPLEQ_EMPTY(&idr_cache.preloaded_nodes),
-           "missing call to idr_preload");
+       if (SIMPLEQ_EMPTY(&idr_cache.preloaded_nodes)) {
+               mutex_spin_exit(&idr_cache.lock);
+               return -ENOMEM;
+       }
        node = SIMPLEQ_FIRST(&idr_cache.preloaded_nodes);
        SIMPLEQ_REMOVE_HEAD(&idr_cache.preloaded_nodes, in_list);
        mutex_spin_exit(&idr_cache.lock);