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hrtimer: fix signed/unsigned bug in slack estimator

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the slack estimator used unsigned math; however for very short delay it's
possible that by the time you calculate the timeout, it's already passed and
you get a negative time/slack... in an unsigned variable... which then gets
turned into a 100 msec delay rather than zero.

This patch fixes this by using a signed typee in the right places.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
This commit is contained in:
Arjan van de Ven 2008-09-07 16:08:55 -07:00
parent 704af52bd1
commit 96d2ab484e
1 changed files with 8 additions and 5 deletions
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13
fs/select.c
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@ -41,9 +41,9 @@
* better solutions.. * better solutions..
*/ */
static unsigned long __estimate_accuracy(struct timespec *tv) static long __estimate_accuracy(struct timespec *tv)
{ {
unsigned long slack; long slack;
int divfactor = 1000; int divfactor = 1000;
if (task_nice(current) > 0) if (task_nice(current) > 0)
@ -54,10 +54,13 @@ static unsigned long __estimate_accuracy(struct timespec *tv)
if (slack > 100 * NSEC_PER_MSEC) if (slack > 100 * NSEC_PER_MSEC)
slack = 100 * NSEC_PER_MSEC; slack = 100 * NSEC_PER_MSEC;
if (slack < 0)
slack = 0;
return slack; return slack;
} }
static unsigned long estimate_accuracy(struct timespec *tv) static long estimate_accuracy(struct timespec *tv)
{ {
unsigned long ret; unsigned long ret;
struct timespec now; struct timespec now;
@ -330,7 +333,7 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
timed_out = 1; timed_out = 1;
} }
if (end_time) if (end_time && !timed_out)
slack = estimate_accuracy(end_time); slack = estimate_accuracy(end_time);
retval = 0; retval = 0;
@ -656,7 +659,7 @@ static int do_poll(unsigned int nfds, struct poll_list *list,
timed_out = 1; timed_out = 1;
} }
if (end_time) if (end_time && !timed_out)
slack = estimate_accuracy(end_time); slack = estimate_accuracy(end_time);
for (;;) { for (;;) {