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authorRobert Richter <robert.richter@amd.com>2010-08-13 16:29:04 +0200
committerRobert Richter <robert.richter@amd.com>2010-08-25 09:09:09 +0200
commit750d857c682f4db60d14722d430c7ccc35070962 (patch)
treebcf6e23fc5dd861104bc4b8309a8ce47aded2d6e /arch/x86/oprofile
parentda5cabf80e2433131bf0ed8993abc0f7ea618c73 (diff)
downloadlinux-2.6.38-lt-ux500-750d857c682f4db60d14722d430c7ccc35070962.tar.gz
oprofile: fix crash when accessing freed task structs
This patch fixes a crash during shutdown reported below. The crash is caused by accessing already freed task structs. The fix changes the order for registering and unregistering notifier callbacks. All notifiers must be initialized before buffers start working. To stop buffer synchronization we cancel all workqueues, unregister the notifier callback and then flush all buffers. After all of this we finally can free all tasks listed. This should avoid accessing freed tasks. On 22.07.10 01:14:40, Benjamin Herrenschmidt wrote: > So the initial observation is a spinlock bad magic followed by a crash > in the spinlock debug code: > > [ 1541.586531] BUG: spinlock bad magic on CPU#5, events/5/136 > [ 1541.597564] Unable to handle kernel paging request for data at address 0x6b6b6b6b6b6b6d03 > > Backtrace looks like: > > spin_bug+0x74/0xd4 > ._raw_spin_lock+0x48/0x184 > ._spin_lock+0x10/0x24 > .get_task_mm+0x28/0x8c > .sync_buffer+0x1b4/0x598 > .wq_sync_buffer+0xa0/0xdc > .worker_thread+0x1d8/0x2a8 > .kthread+0xa8/0xb4 > .kernel_thread+0x54/0x70 > > So we are accessing a freed task struct in the work queue when > processing the samples. Reported-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: stable@kernel.org Signed-off-by: Robert Richter <robert.richter@amd.com>
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