diff options
| author | cinap_lenrek <cinap_lenrek@felloff.net> | 2014-08-16 21:04:41 +0200 |
|---|---|---|
| committer | cinap_lenrek <cinap_lenrek@felloff.net> | 2014-08-16 21:04:41 +0200 |
| commit | 773b57b676526975059e5ba3858cfde6d8b50ceb (patch) | |
| tree | e0c4d5e398cb1b2665ba1966dbbeae666f8c9ad0 | |
| parent | ce0b77e2b9bd4669844d0356f8e49d2f4878bac8 (diff) | |
kernel: fix todfix() race
we have to recheck the condition under tod lock, otherwise
another process can come in and updated tod.last and
tod.off and once we have the lock, we would make time
jump backwards.
| -rw-r--r-- | sys/src/9/port/tod.c | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/sys/src/9/port/tod.c b/sys/src/9/port/tod.c index 424e0f290..b88f721af 100644 --- a/sys/src/9/port/tod.c +++ b/sys/src/9/port/tod.c @@ -198,11 +198,13 @@ todfix(void) uvlong x; ticks = fastticks(nil); + diff = ticks - tod.last; + if(diff <= tod.hz) + return; + ilock(&tod); diff = ticks - tod.last; if(diff > tod.hz){ - ilock(&tod); - /* convert to epoch */ mul64fract(&x, diff, tod.multiplier); if(x > 30000000000ULL) iprint("todfix %llud\n", x); @@ -211,9 +213,8 @@ if(x > 30000000000ULL) iprint("todfix %llud\n", x); /* protect against overflows */ tod.last = ticks; tod.off = x; - - iunlock(&tod); } + iunlock(&tod); } long |