--- ll_rw_blk.c.old Wed Nov 20 15:32:50 2002
+++ ll_rw_blk.c Wed Nov 20 15:33:06 2002
@@ -2092,7 +2092,7 @@
complete(req->waiting);
if (disk) {
- unsigned long duration = jiffies - req->start_time;
+ unsigned long duration = (signed) jiffies - (signed) req->start_time;
switch (rq_data_dir(req)) {
case WRITE:
disk->writes++;
On Wed, 2002-11-20 at 20:44, Luben Tuikov wrote:
> --- ll_rw_blk.c.old Wed Nov 20 15:32:50 2002
> +++ ll_rw_blk.c Wed Nov 20 15:33:06 2002
> @@ -2092,7 +2092,7 @@
> complete(req->waiting);
>
> if (disk) {
> - unsigned long duration = jiffies - req->start_time;
> + unsigned long duration = (signed) jiffies - (signed) req->start_time;
> switch (rq_data_dir(req)) {
It was right before. Your patch breaks it. Think about it in unsigned
maths
0x00000002 - 0xFFFFFFFF = 0x00000003
Alan
Alan Cox wrote:
>
> On Wed, 2002-11-20 at 20:44, Luben Tuikov wrote:
> > --- ll_rw_blk.c.old Wed Nov 20 15:32:50 2002
> > +++ ll_rw_blk.c Wed Nov 20 15:33:06 2002
> > @@ -2092,7 +2092,7 @@
> > complete(req->waiting);
> >
> > if (disk) {
> > - unsigned long duration = jiffies - req->start_time;
> > + unsigned long duration = (signed) jiffies - (signed) req->start_time;
> > switch (rq_data_dir(req)) {
>
> It was right before. Your patch breaks it. Think about it in unsigned
> maths
>
> 0x00000002 - 0xFFFFFFFF = 0x00000003
0x2 - (-0x1) = 0x2 + 0x1 = 0x3
Right! I thought (signed) does the job. I actually tried
it both ways and works all right. I guess either way works fine.
--
Luben
On Wed, 2002-11-20 at 21:00, Luben Tuikov wrote:sk) {
> > > - unsigned long duration = jiffies - req->start_time;
> > > + unsigned long duration = (signed) jiffies - (signed) req->start_time;
> > > switch (rq_data_dir(req)) {
> >
> > It was right before. Your patch breaks it. Think about it in unsigned
> > maths
> >
> > 0x00000002 - 0xFFFFFFFF = 0x00000003
>
> 0x2 - (-0x1) = 0x2 + 0x1 = 0x3
>
> Right! I thought (signed) does the job. I actually tried
> it both ways and works all right. I guess either way works fine.
(signed long) maybe - but not signed - long is 64bit on Alpha, (signed)
is 32
Erm, you just truncated a long to an int.
-ben
On Wed, Nov 20, 2002 at 03:44:03PM -0500, Luben Tuikov wrote:
> --- ll_rw_blk.c.old Wed Nov 20 15:32:50 2002
> +++ ll_rw_blk.c Wed Nov 20 15:33:06 2002
> @@ -2092,7 +2092,7 @@
> complete(req->waiting);
>
> if (disk) {
> - unsigned long duration = jiffies - req->start_time;
> + unsigned long duration = (signed) jiffies - (signed) req->start_time;
> switch (rq_data_dir(req)) {
> case WRITE:
> disk->writes++;
> -
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--
"Do you seek knowledge in time travel?"
Benjamin LaHaise wrote:
>
> Erm, you just truncated a long to an int.
Yep, totally forgot about no type == int, hehehhee.
Boy, last time I thought about that _rule_ was over 12 years ago...
--
Luben
Alan Cox wrote:
>
> On Wed, 2002-11-20 at 21:00, Luben Tuikov wrote:sk) {
> > > > - unsigned long duration = jiffies - req->start_time;
> > > > + unsigned long duration = (signed) jiffies - (signed) req->start_time;
> > > > switch (rq_data_dir(req)) {
> > >
> > > It was right before. Your patch breaks it. Think about it in unsigned
> > > maths
> > >
> > > 0x00000002 - 0xFFFFFFFF = 0x00000003
> >
> > 0x2 - (-0x1) = 0x2 + 0x1 = 0x3
> >
> > Right! I thought (signed) does the job. I actually tried
> > it both ways and works all right. I guess either way works fine.
>
> (signed long) maybe - but not signed - long is 64bit on Alpha, (signed)
> is 32
Aaaah, I see where you're coming from.
I basically tried to stay away from knowing _what_ actual
type it is and just to make it signed and do the arithmetic,
but didn't know the specific for the Alpha.
Shouldn't this be (symbolically:) (signed (typeof(jiffes)) jiffies -
(signed (typeof(start)) start -- you know what I mean.
But yes both ways should work:
a, b are both unsigned, then a-b = a+(-b) and there's just no
other way to compute the result.
Anyway, doesn't matter,
--
Luben
On Wed, Nov 20, 2002 at 09:19:33PM +0000, Alan Cox wrote:
> On Wed, 2002-11-20 at 20:44, Luben Tuikov wrote:
> > --- ll_rw_blk.c.old Wed Nov 20 15:32:50 2002
> > +++ ll_rw_blk.c Wed Nov 20 15:33:06 2002
> > @@ -2092,7 +2092,7 @@
> > complete(req->waiting);
> >
> > if (disk) {
> > - unsigned long duration = jiffies - req->start_time;
> > + unsigned long duration = (signed) jiffies - (signed) req->start_time;
> > switch (rq_data_dir(req)) {
>
> It was right before. Your patch breaks it. Think about it in unsigned
> maths
>
> 0x00000002 - 0xFFFFFFFF = 0x00000003
Signed vs. unsigned is actually irrelevant in two-complement systems
as long as you don't compare. Only the int/long issue has an actual
effect.
OG.