lkml.org 
[lkml]   [2000]   [Jan]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: (*(unsigned long *)&jiffies)++;
Date
From: "Tigran Aivazian" <tigran@sco.COM>
> On Thu, 6 Jan 2000, Petko Manolov wrote:
> > Exactly.
> > "(*(unsigned long *)&jiffies)++" did just "incl jiffies"
> > at the time and in the place you write it.
>
> Ok. Why is it not done for lost_ticks and lost_ticks_system?
>
I don't know. I just checked my source archive: linux-1.2.13 uses
"jiffies++", and 2.0.38 uses "(*(...))".

I don't know why this cast was added, but it doesn't enforce atomicity on
SMP computers. _If_ we really need the atomicity, then something like this
could fix the problem:

- unsigned long volatile jiffies = 0;
+atomic_t atomic_jiffies = ATOMIC_INIT(0);

+ #define INC_JIFFIES() atomic_inc(&atomic_jiffies);
+ #defien ADD_JIFFIES(inc) atomci_add(&atomic_jiffies,inc);
+ #define jiffies ((unsigned long) atomic_get(&atomic_jiffies));

Warning: I never tried that, I didn't check if it will be correct on 64-bit
archs, ...

--
Manfred


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:55    [W:0.113 / U:0.216 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site