some atomic operations are only atomic, not ordered. Thus a CPU is allowed
to reorder memory references to an object to before the reference is
obtained. This fixes it.
Signed-off-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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>
Avoid an atomic operation in kref_put() when the last reference is
dropped. On most platforms, atomic_read() is a plan read of the counter
and involves no atomic at all.
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Oliver Neukum