On 04/05/2014 09:35 AM, Rafał Miłecki wrote:
Register B43_MMIO_PSM_PHY_HDR is 16 bit one, so accessing it with 32b functions isn't safe. On my machine it causes delayed (!) CPU exception: Disabling lock debugging due to kernel taint mce: [Hardware Error]: CPU 0: Machine Check Exception: 4 Bank 4: b200000000070f0f mce: [Hardware Error]: TSC 164083803dc mce: [Hardware Error]: PROCESSOR 2:20fc2 TIME 1396650505 SOCKET 0 APIC 0 microcode 0 mce: [Hardware Error]: Run the above through 'mcelog --ascii' mce: [Hardware Error]: Machine check: Processor context corrupt Kernel panic - not syncing: Fatal machine check on current CPU Kernel Offset: 0x0 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffff9fffffff) Signed-off-by: Rafał Miłecki <zajec5@xxxxxxxxx> --- John: I think this patch it worth picking for 3.15 release. This bug causes instability and can be triggered depending on the default state of B43_NPHY_BANDCTL register. It doesn't cause exception immediately, so I spent few hours tracing it. ---
I agree that this is a BUG fix that should be in 3.15, *and* in all stable versions to which it would apply.
To aid John, I suggest that a better subject would be something like "b43: Fix machine check error due to improper access of B43_MMIO_PSM_PHY_HDR". That makes it more obvious that a bug is being fixed. In addition, you should add a "Cc: Stable <stable@xxxxxxxxxxxxxxx> [2.6.35+]".
As I rarely run an 802.11n Broadcom device, it is unlikely that I have encountered this problem, but your evidence is convincing. Once the subject and Cc are changed, then Acked-by: Larry Finger <Larry.Finger@xxxxxxxxxxxx>
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