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SubjectRe: Wireless IBSS on Linux-2.6.34 broken by commit 3bbb9ec946428b96657126768f65487a48dd090c


On Mon, May 24, 2010 at 10:57 PM, Linus Torvalds <torvalds@linux-foundation.org> wrote:>
> On Mon, 24 May 2010, Jeff Chua wrote:
>> + if (timer->slack > -1)
>> + else if (time_after(expires, jiffies)) /* auto slack: use 0.4% */
>> expires_limit = expires + (expires - jiffies)/256;
>
> Please don't reload 'jiffies' twice. It's volatile, and the compiler will
> do a crap job of it.

Linus,

Sorry, didn't know what a jiffies was before, so didn't know about the
crap it caused. Now I learned something new.

> Also, '0' is a normal number, but '-1' is a rather odd value. Please just
> test for non-negative by doing ">= 0" rather than "> -1"

Fixed.

Below is the patch to fix jiffies and checking for non-negative.


Thanks,
Jeff

--- a/kernel/timer.c.org 2010-05-25 06:05:46.000000000 +0800
+++ a/kernel/timer.c 2010-05-25 06:17:44.000000000 +0800
@@ -748,14 +748,15 @@
unsigned long apply_slack(struct timer_list *timer, unsigned long expires)
{
unsigned long expires_limit, mask;
+ unsigned long now = jiffies;
int bit;

expires_limit = expires;

- if (timer->slack > -1)
+ if (timer->slack >= 0)
expires_limit = expires + timer->slack;
- else if (time_after(expires, jiffies)) /* auto slack: use 0.4% */
- expires_limit = expires + (expires - jiffies)/256;
+ else if (time_after(expires, now)) /* auto slack: use 0.4% */
+ expires_limit = expires + (expires - now)/256;

mask = expires ^ expires_limit;
if (mask == 0)


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