Skip to contentSkip to conversation

Patch "[PKT_SCHED]: PSCHED_TADD() and PSCHED_TADD2() can result,tv_usec >= 1000000" seems wrong

PATCH Applied Guillaume Chazarain 3 participants 4 messages Jul 14, 2006 – Jul 24, 2006

Subsystems (3)
Networking Network drivers Traffic control (tc)
lore
Share & tools
lore

Guillaume Chazarain

author
#0 lore raw

Hello,

This patch:
http://www.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=4ee303dfeac6451b402e3d8512723d3a0f861857

looks wrong.

In PSCHED_TADD2, if delta is less than tv.tv_usec (so, less than USEC_PER_SEC too) then tv_res will be before tv. The affectation (tv_res).tv_usec = __delta; is wrong. The same applies to PSCHED_TADD.

I think the correct fix is simply to restore the original code and change the 'if' in a 'while'.

So here are two patches for the two possible solutions :

o Reverting the commit and applying from_before_patch_to_correct.diff

o Applying from_tip_to_correct.diff

Thanks.

Signature · 1 line
Guillaume
include/net/pkt_sched.h renamed from include/net/pkt_sched.h.before +2 -2
@@ -171,14 +171,14 @@
 ({ \
 	   int __delta = (tv).tv_usec + (delta); \
 	   (tv_res).tv_sec = (tv).tv_sec; \
-	   if (__delta > USEC_PER_SEC) { (tv_res).tv_sec++; __delta -= USEC_PER_SEC; } \
+	   while (__delta > USEC_PER_SEC) { (tv_res).tv_sec++; __delta -= USEC_PER_SEC; } \
 	   (tv_res).tv_usec = __delta; \
 })
 
 #define PSCHED_TADD(tv, delta) \
 ({ \
 	   (tv).tv_usec += (delta); \
-	   if ((tv).tv_usec > USEC_PER_SEC) { (tv).tv_sec++; \
+	   while ((tv).tv_usec > USEC_PER_SEC) { (tv).tv_sec++; \
 		 (tv).tv_usec -= USEC_PER_SEC; } \
 })
Signature · 1 line
Signed-off-by: Guillaume Chazarain <[email protected]>
include/net/pkt_sched.h +6 -12
diff -r 672dc37bf355 include/net/pkt_sched.h
@@ -169,23 +169,17 @@ psched_tod_diff(int delta_sec, int bound
 
 #define PSCHED_TADD2(tv, delta, tv_res) \
 ({ \
-	   int __delta = (delta); \
-	   (tv_res) = (tv); \
-	   while(__delta >= USEC_PER_SEC){ \
-		 (tv_res).tv_sec++; \
-		 __delta -= USEC_PER_SEC; \
-	   } \
+	   int __delta = (tv).tv_usec + (delta); \
+	   (tv_res).tv_sec = (tv).tv_sec; \
+	   while (__delta > USEC_PER_SEC) { (tv_res).tv_sec++; __delta -= USEC_PER_SEC; } \
 	   (tv_res).tv_usec = __delta; \
 })
 
 #define PSCHED_TADD(tv, delta) \
 ({ \
-	   int __delta = (delta); \
-	   while(__delta >= USEC_PER_SEC){ \
-		 (tv).tv_sec++; \
-		 __delta -= USEC_PER_SEC; \
-	   } \
-	   (tv).tv_usec = __delta; \
+	   (tv).tv_usec += (delta); \
+	   while ((tv).tv_usec > USEC_PER_SEC) { (tv).tv_sec++; \
+		 (tv).tv_usec -= USEC_PER_SEC; } \
 })
 
 /* Set/check that time is in the "past perfect";
Signature · 1 line
Signed-off-by: Guillaume Chazarain <[email protected]>
#1 lore raw

Hello.

Quoted 2 lines

In PSCHED_TADD2, if delta is less than tv.tv_usec (so, less than USEC_PER_SEC too) then tv_res will be before tv. The affectation (tv_res).tv_usec = __delta; is wrong. The same applies to PSCHED_TADD.

You are right. It is my mistake.

Quoted 1 line

I think the correct fix is simply to restore the original code and change the 'if' in a 'while'.

In Guillaume's patch,
"while (__delta > USEC_PER_SEC){ ... }", but I think it should be "while (__delta >= USEC_PER_SEC){ ... }". Is it right?

Thank you very much.

Signature · 1 line
Shuya MAEDA
author
#2 lore raw
Quoted 2 lines · Shuya MAEDA

"while (__delta > USEC_PER_SEC){ ... }", but I think it should be "while (__delta >= USEC_PER_SEC){ ... }". Is it right?

I agree, good catch :-)

Thanks.

Signature · 1 line
Guillaume

In PSCHED_TADD and PSCHED_TADD2, if delta is less than tv.tv_usec (so, less than USEC_PER_SEC too) then tv_res will be smaller than tv. The affectation "(tv_res).tv_usec = __delta;" is wrong.
The fix is to revert to the original code before 4ee303dfeac6451b402e3d8512723d3a0f861857 and change the 'if' in 'while'.

[Shuya MAEDA: "while (__delta >= USEC_PER_SEC){ ... }" instead of "while (__delta > USEC_PER_SEC){ ... }"]

Signed-off-by Guillaume Chazarain <[email protected]>

---

 pkt_sched.h |   18 ++++++------------
 1 file changed, 6 insertions(+), 12 deletions(-)
include/net/pkt_sched.h +6 -12
@@ -169,23 +169,17 @@ psched_tod_diff(int delta_sec, int bound
 
 #define PSCHED_TADD2(tv, delta, tv_res) \
 ({ \
-	   int __delta = (delta); \
-	   (tv_res) = (tv); \
-	   while(__delta >= USEC_PER_SEC){ \
-		 (tv_res).tv_sec++; \
-		 __delta -= USEC_PER_SEC; \
-	   } \
+	   int __delta = (tv).tv_usec + (delta); \
+	   (tv_res).tv_sec = (tv).tv_sec; \
+	   while (__delta >= USEC_PER_SEC) { (tv_res).tv_sec++; __delta -= USEC_PER_SEC; } \
 	   (tv_res).tv_usec = __delta; \
 })
 
 #define PSCHED_TADD(tv, delta) \
 ({ \
-	   int __delta = (delta); \
-	   while(__delta >= USEC_PER_SEC){ \
-		 (tv).tv_sec++; \
-		 __delta -= USEC_PER_SEC; \
-	   } \
-	   (tv).tv_usec = __delta; \
+	   (tv).tv_usec += (delta); \
+	   while ((tv).tv_usec >= USEC_PER_SEC) { (tv).tv_sec++; \
+		 (tv).tv_usec -= USEC_PER_SEC; } \
 })
 
 /* Set/check that time is in the "past perfect";
maintainer Applied
#3 lore raw

From: Guillaume Chazarain <[email protected]>
Date: Wed, 19 Jul 2006 14:47:34 +0200

Quoted 5 lines
Quoted 2 lines · Shuya MAEDA

"while (__delta > USEC_PER_SEC){ ... }", but I think it should be "while (__delta >= USEC_PER_SEC){ ... }". Is it right?

I agree, good catch :-)

Applied, thanks a lot.