Warnings from sched_debug.c

Warnings from sched_debug.c

[Meelis Roos]

This happens on sparc64 with 2.6.24-rc6 (gcc-4.2):

  CC      kernel/sched.o
In file included from kernel/sched.c:879:
kernel/sched_debug.c: In function 'nsec_high':
kernel/sched_debug.c:38: warning: comparison of distinct pointer types lacks a cast
kernel/sched_debug.c:41: warning: comparison of distinct pointer types lacks a cast
kernel/sched_debug.c: In function 'nsec_low':
kernel/sched_debug.c:51: warning: comparison of distinct pointer types lacks a cast


-- 
Meelis Roos (mroos@linux.ee)

Re: Warnings from sched_debug.c

[Ingo Molnar]

* Meelis Roos <mroos@linux.ee> wrote:

> This happens on sparc64 with 2.6.24-rc6 (gcc-4.2):
> 
>   CC      kernel/sched.o
> In file included from kernel/sched.c:879:
> kernel/sched_debug.c: In function 'nsec_high':
> kernel/sched_debug.c:38: warning: comparison of distinct pointer types lacks a cast
> kernel/sched_debug.c:41: warning: comparison of distinct pointer types lacks a cast
> kernel/sched_debug.c: In function 'nsec_low':
> kernel/sched_debug.c:51: warning: comparison of distinct pointer types lacks a cast

it should be harmless. Does the patch below fix the warnings?

	Ingo

-------------->
Subject: sched: fix gcc warnings
From: Ingo Molnar <mingo@elte.hu>

Meelis Roos reported these warnings on sparc64:

  CC      kernel/sched.o
  In file included from kernel/sched.c:879:
  kernel/sched_debug.c: In function 'nsec_high':
  kernel/sched_debug.c:38: warning: comparison of distinct pointer types lacks a cast

the debug check in do_div() is over-eager here, because the long long
is always positive in these places. Mark this by casting them to
unsigned long long.

no change in code output:

   text    data     bss     dec     hex filename
  51471    6582     376   58429    e43d sched.o.before
  51471    6582     376   58429    e43d sched.o.after

  md5:
   7f7729c111f185bf3ccea4d542abc049  sched.o.before.asm
   7f7729c111f185bf3ccea4d542abc049  sched.o.after.asm

Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 kernel/sched_debug.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

Index: linux/kernel/sched_debug.c
===================================================================
--- linux.orig/kernel/sched_debug.c
+++ linux/kernel/sched_debug.c
@@ -31,9 +31,9 @@
 /*
  * Ease the printing of nsec fields:
  */
-static long long nsec_high(long long nsec)
+static long long nsec_high(unsigned long long nsec)
 {
-	if (nsec < 0) {
+	if ((long long)nsec < 0) {
 		nsec = -nsec;
 		do_div(nsec, 1000000);
 		return -nsec;
@@ -43,9 +43,9 @@ static long long nsec_high(long long nse
 	return nsec;
 }
 
-static unsigned long nsec_low(long long nsec)
+static unsigned long nsec_low(unsigned long long nsec)
 {
-	if (nsec < 0)
+	if ((long long)nsec < 0)
 		nsec = -nsec;
 
 	return do_div(nsec, 1000000);

Re: Warnings from sched_debug.c

[Meelis Roos]

> it should be harmless. Does the patch below fix the warnings?

Yes, the warnings are gone, thanks!

However, I found another somewhat strange thing while testing it - 
touching kernels/sched_debug.c does not cause a recompile since 
sched_debug.c is only #included from sched.c. Found it because I was 
looking for sched_debug.o recompile.

-- 
Meelis Roos (mroos@linux.ee)