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4f84e4be53
Background:
When a userspace application wants to know about machine check events, it
opens /dev/mcelog and does a read(). Usually, we found that this interface
works well, but in some cases, when the system was taking large numbers of
machine check exceptions, the read() would hang. The system would output a
soft-lockup warning, and the daemon reading from /dev/mcelog would suck up
as much of a single CPU as it could spinning in system space.
Description:
This patch fixes this bug. In particular, there was a "continue" inside a
timeout loop that presumably was intended to break out of the outer loop,
but instead caused the inner loop to continue. This patch also makes the
condition for the break-out a little more evident by changing a
!time_before to a time_after_eq.
Result:
The read() no longer hangs in this test case.
Testing:
On my system, I could replicate the bug with the following command:
# for i in `seq 15000`; do ./inject_sbe.sh; done
where inject_sbe.sh contains commands to inject a single-bit error into the
next memory write transaction.
Patch:
This patch is against git
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| .. | ||
| boot | ||
| crypto | ||
| ia32 | ||
| kernel | ||
| lib | ||
| mm | ||
| oprofile | ||
| pci | ||
| defconfig | ||
| Kconfig | ||
| Kconfig.debug | ||
| Makefile | ||