Messages in this thread Patch in this message | | | Date | Tue, 14 Feb 2006 11:56:08 +0100 | From | Heiko Carstens <> | Subject | Re: calibrate_migration_costs takes ages on s390 |
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> I did a quick git bisect search. This is one is the hurting one: > > Author: Ingo Molnar <mingo@elte.hu> 2006-02-07 21:58:54 > Committer: Linus Torvalds <torvalds@g5.osdl.org> 2006-02-08 01:12:33 > Parent: 8519fb30e438f8088b71a94a7d5a660a814d3872 ([PATCH] mm: compound release fix) > Child: 0d4c3e7a8c65892c7d6a748fdbb4499e988880db ([PATCH] unshare system call -v5: Documentation file) > > The fix is to include a __delay(1) call in the loop, to correctly approximate > the intended delay timeout of 1 second. The code assumes that every > architecture implements __delay(1) to last around 1/(loops_per_jiffy*HZ) > seconds. > > I guess we're once again suffering from being a virtualized platform: the > formerly used call to cpu_relax() informed the underlying hypervisor that > we want to give up the current cpu while __delay() keeps it. > Unless we're scheduled away involuntarily. > The "Detect Soft Lockups" option doesn't make too much sense too on our > platform, since we get a lot of false positives. > Quick fix: turn off the options CONFIG_DEBUG_SPINLOCK and > CONFIG_DETECT_SOFTLOCKUP.
Wrong analysis. Our __delay() implementation is broken. This doesn't help for the CONFIG_DETECT_SOFTLOCKUP case, but at least CONFIG_DEBUG_SPINLOCK works again with this.
Andrew, could you pick this one up, or should I send it separately?
[PATCH] s390: fix __delay implementation
From: Heiko Carstens <heiko.carstens@de.ibm.com>
Fix __delay implementation. Called with an argument "1" or "0" it would loop nearly forever (since (1/2)-1 = 0xffffffff).
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> ---
arch/s390/lib/delay.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/s390/lib/delay.c b/arch/s390/lib/delay.c index e96c35b..71f0a2f 100644 --- a/arch/s390/lib/delay.c +++ b/arch/s390/lib/delay.c @@ -30,7 +30,7 @@ void __delay(unsigned long loops) */ __asm__ __volatile__( "0: brct %0,0b" - : /* no outputs */ : "r" (loops/2) ); + : /* no outputs */ : "r" ((loops/2) + 1)); } /* - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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