mirror of
https://github.com/torvalds/linux.git
synced 2024-12-23 03:11:46 +00:00
9eb3394bf2
Ensure a consistent value is read from the STICK register by ensuring that both high and low are read without high changing due to a roll over of the low register. Various Debian/SPARC users (myself include) have noticed problems with Hummingbird based systems. The symptoms are that the system time is seen to jump forward 3 days, 6 hours, 11 minutes give or take a few seconds. In many cases the system then hangs some time afterwards. I've spotted a race condition in the code to read the STICK register. I could not work out why 3d, 6h, 11m is important but guess that it is due to the 2^32 jump of STICK (forwards on one read and then the next read will seem to be backwards) during a timer interrupt. I'm guessing that a change of -2^32 will get converted to a large unsigned increment after the arithmetic manipulation between STICK, nanoseconds, jiffies etc. I did a test where I modified __hbird_read_stick to artificially inject rollover faults forcefully every few seconds. With this I saw the clock jump over 6 times in 12 hours compared to once every month or so. Signed-off-by: Richard Mortimer <richm@oldelvet.org.uk> Signed-off-by: David S. Miller <davem@davemloft.net> |
||
|---|---|---|
| .. | ||
| boot | ||
| kernel | ||
| lib | ||
| math-emu | ||
| mm | ||
| oprofile | ||
| prom | ||
| solaris | ||
| defconfig | ||
| Kconfig | ||
| Kconfig.debug | ||
| Makefile | ||