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authorVenkatesh Pallipadi <venkatesh.pallipadi@intel.com>2006-12-19 13:01:29 -0800
committerGreg Kroah-Hartman <gregkh@suse.de>2006-12-20 10:56:43 -0800
commitf334b60b43a0927f4ab1187cbdb4582f5227c3b1 (patch)
tree1ee4de7327b894c290a60a415a8bdc111fe046b7 /lib
parentMerge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/hid (diff)
downloadlinux-dev-f334b60b43a0927f4ab1187cbdb4582f5227c3b1.tar.xz
linux-dev-f334b60b43a0927f4ab1187cbdb4582f5227c3b1.zip
kref refcnt and false positives
With WARN_ON addition to kobject_init() [ http://kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.19/2.6.19-mm1/dont-use/broken-out/gregkh-driver-kobject-warn.patch ] I started seeing following WARNING on CPU offline followed by online on my x86_64 system. WARNING at lib/kobject.c:172 kobject_init() Call Trace: [<ffffffff8020ab45>] dump_trace+0xaa/0x3ef [<ffffffff8020aec4>] show_trace+0x3a/0x50 [<ffffffff8020b0f6>] dump_stack+0x15/0x17 [<ffffffff80350abc>] kobject_init+0x3f/0x8a [<ffffffff80350be1>] kobject_register+0x1a/0x3e [<ffffffff803bbd89>] sysdev_register+0x5b/0xf9 [<ffffffff80211d0b>] mce_create_device+0x77/0xf4 [<ffffffff80211dc2>] mce_cpu_callback+0x3a/0xe5 [<ffffffff805632fd>] notifier_call_chain+0x26/0x3b [<ffffffff8023f6f3>] raw_notifier_call_chain+0x9/0xb [<ffffffff802519bf>] _cpu_up+0xb4/0xdc [<ffffffff80251a12>] cpu_up+0x2b/0x42 [<ffffffff803bef00>] store_online+0x4a/0x72 [<ffffffff803bb6ce>] sysdev_store+0x24/0x26 [<ffffffff802baaa2>] sysfs_write_file+0xcf/0xfc [<ffffffff8027fc6f>] vfs_write+0xae/0x154 [<ffffffff80280418>] sys_write+0x47/0x6f [<ffffffff8020963e>] system_call+0x7e/0x83 DWARF2 unwinder stuck at system_call+0x7e/0x83 Leftover inexact backtrace: This is a false positive as mce.c is unregistering/registering sysfs interfaces cleanly on hotplug. kref_put() and conditional decrement of refcnt seems to be the root cause for this and the patch below resolves the issue for me. Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'lib')
-rw-r--r--lib/kref.c7
1 files changed, 1 insertions, 6 deletions
diff --git a/lib/kref.c b/lib/kref.c
index 4a467faf1367..0d07cc31c818 100644
--- a/lib/kref.c
+++ b/lib/kref.c
@@ -52,12 +52,7 @@ int kref_put(struct kref *kref, void (*release)(struct kref *kref))
WARN_ON(release == NULL);
WARN_ON(release == (void (*)(struct kref *))kfree);
- /*
- * if current count is one, we are the last user and can release object
- * right now, avoiding an atomic operation on 'refcount'
- */
- if ((atomic_read(&kref->refcount) == 1) ||
- (atomic_dec_and_test(&kref->refcount))) {
+ if (atomic_dec_and_test(&kref->refcount)) {
release(kref);
return 1;
}