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SubjectRe: [PATCH 1/5] Skip timer works.patch
* Andrew Morton (akpm@osdl.org) wrote:
> Andi seems to have merged this patch but from somewhere I picked up a
> different version, below.

That was from me. The earlier one had fallen through the cracks, so
I picked it up and reworked it (so that it uses no_timer_check) as per
Andi's suggestion.

> I think the version I have is better.

Agreed ;-)

> Because the patch Andi has merged is
> cast in terms of "irq testing", which is broad. But that's not what the
> patch does - the patch handles only timers.
>
> IOW, this:
>
> > +
> > + noirqtest [IA-32,APIC] Disables the code which tests for broken
> > + timer IRQ sources.
>
> is misleadingly named. This:
>
> + no_timer_check [IA-32,X86_64,APIC] Disables the code which tests for
> + broken timer IRQ sources.
> +
>
> is better, no?

Clearer, and also same as x86_64.

> But right now, I'll settle for anything which usually compiles.

I believe the current round has fixed all the know compilation issues.
There's one outstanding runtime issue from Andi, which I believe is due
to an old glibc which requires COMPAT_VDSO (and which CONFIG_PARAVIRT
must disable). So current set is clean from the reports I have (and
assuming above vdso analysis is correct).

thanks,
-chris
--
> From: Zachary Amsden <zach@vmware.com>
>
> Add a way to disable the timer IRQ routing check via a boot option. The
> VMI timer code uses this to avoid triggering the pester Mingo code, which
> probes for some very unusual and broken motherboard routings. It fires
> 100% of the time when using a paravirtual delay mechanism instead of using
> a realtime delay, since there is no elapsed real time, and the 4 timer IRQs
> have not yet been delivered.
>
> In addition, it is entirely possible, though improbable, that this bug
> could surface on real hardware which picks a particularly bad time to enter
> SMM mode, causing a long latency during one of the timer IRQs.
>
> While here, make check_timer be __init.
>
> Signed-off-by: Zachary Amsden <zach@vmware.com>
> [chrisw: use no_timer_check to bring inline with x86_64 as per Andi's request]
> Signed-off-by: Chris Wright <chrisw@sous-sol.org>
> Cc: Andi Kleen <ak@suse.de>
> Signed-off-by: Andrew Morton <akpm@osdl.org>
> ---
>
> Documentation/kernel-parameters.txt | 7 +++++--
> arch/i386/kernel/io_apic.c | 16 ++++++++++++++--
> 2 files changed, 19 insertions(+), 4 deletions(-)
>
> diff -puN arch/i386/kernel/io_apic.c~i386-add-a-way-to-disable-the-timer-irq-routing-check-via-a-boot-option arch/i386/kernel/io_apic.c
> --- a/arch/i386/kernel/io_apic.c~i386-add-a-way-to-disable-the-timer-irq-routing-check-via-a-boot-option
> +++ a/arch/i386/kernel/io_apic.c
> @@ -1930,6 +1930,15 @@ static void __init setup_ioapic_ids_from
> static void __init setup_ioapic_ids_from_mpc(void) { }
> #endif
>
> +static int no_timer_check __initdata;
> +
> +static int __init notimercheck(char *s)
> +{
> + no_timer_check = 1;
> + return 1;
> +}
> +__setup("no_timer_check", notimercheck);
> +
> /*
> * There is a nasty bug in some older SMP boards, their mptable lies
> * about the timer IRQ. We do the following to work around the situation:
> @@ -1938,10 +1947,13 @@ static void __init setup_ioapic_ids_from
> * - if this function detects that timer IRQs are defunct, then we fall
> * back to ISA timer IRQs
> */
> -static int __init timer_irq_works(void)
> +int __init timer_irq_works(void)
> {
> unsigned long t1 = jiffies;
>
> + if (no_timer_check)
> + return 1;
> +
> local_irq_enable();
> /* Let ten ticks pass... */
> mdelay((10 * 1000) / HZ);
> @@ -2212,7 +2224,7 @@ int timer_uses_ioapic_pin_0;
> * is so screwy. Thanks to Brian Perkins for testing/hacking this beast
> * fanatically on his truly buggy board.
> */
> -static inline void check_timer(void)
> +static inline void __init check_timer(void)
> {
> int apic1, pin1, apic2, pin2;
> int vector;
> diff -puN Documentation/kernel-parameters.txt~i386-add-a-way-to-disable-the-timer-irq-routing-check-via-a-boot-option Documentation/kernel-parameters.txt
> --- a/Documentation/kernel-parameters.txt~i386-add-a-way-to-disable-the-timer-irq-routing-check-via-a-boot-option
> +++ a/Documentation/kernel-parameters.txt
> @@ -599,8 +599,6 @@ and is between 256 and 4096 characters.
>
> hugepages= [HW,IA-32,IA-64] Maximal number of HugeTLB pages.
>
> - noirqbalance [IA-32,SMP,KNL] Disable kernel irq balancing
> -
> i8042.direct [HW] Put keyboard port into non-translated mode
> i8042.dumbkbd [HW] Pretend that controller can only read data from
> keyboard and cannot control its state
> @@ -1056,9 +1054,14 @@ and is between 256 and 4096 characters.
> in certain environments such as networked servers or
> real-time systems.
>
> + noirqbalance [IA-32,SMP,KNL] Disable kernel irq balancing
> +
> noirqdebug [IA-32] Disables the code which attempts to detect and
> disable unhandled interrupt sources.
>
> + no_timer_check [IA-32,X86_64,APIC] Disables the code which tests for
> + broken timer IRQ sources.
> +
> noisapnp [ISAPNP] Disables ISA PnP code.
>
> noinitrd [RAM] Tells the kernel not to load any configured
> _
-
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