Re: MIPS: Test reault for enable interrupts before WAIT instruction patch

David Daney
2013-05-07T17:07:33Z

On 05/06/2013 11:30 PM, EUNBONG SONG wrote:
>
> Hello. I tested with two patches.
> The first one is thomas gleixner's patch. The patch is as follow.
> This patch works well without any problem.

You don't need them both. When we fix it, it will be one or the other,
not both.

>
> Index: linux-2.6/arch/mips/kernel/process.c
> ===================================================================
> --- linux-2.6.orig/arch/mips/kernel/process.c
> +++ linux-2.6/arch/mips/kernel/process.c
> @@ -50,13 +50,18 @@ void arch_cpu_idle_dead(void)
> }
> #endif
>
> -void arch_cpu_idle(void)
> +static void smtc_idle_hook(void)
> {
> #ifdef CONFIG_MIPS_MT_SMTC
> extern void smtc_idle_loop_hook(void);
> -
> smtc_idle_loop_hook();
> #endif
> +}
> +
> +void arch_cpu_idle(void)
> +{
> + local_irq_enable();
> + smtc_idle_hook();
> if (cpu_wait)
> (*cpu_wait)();
> else

Although I wrote the other patch, I now think that Thomas Gleixner's
patch (above), is the best option.

There are many cpu_wait() implementations. Fixing a bunch of different
assembly implementations, most of which I cannot test, is a recipe for
disaster.

> --
>
> The second one is david daney's patch. The patch is as follow.
> arch/mips/kernel/genex.S | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/arch/mips/kernel/genex.S b/arch/mips/kernel/genex.S
> index ecb347c..57cda9a 100644
> --- a/arch/mips/kernel/genex.S
> +++ b/arch/mips/kernel/genex.S
> @@ -132,12 +132,13 @@ LEAF(r4k_wait)
> .set noreorder
> /* start of rollback region */
> LONG_L t0, TI_FLAGS($28)
> - nop
> andi t0, _TIF_NEED_RESCHED
> bnez t0, 1f
> nop
> - nop
> - nop
> + /* Enable interrupts so WAIT will complete */
> + mfc0 t0, CP0_STATUS
> + ori t0, ST0_IE
> + mtc0 t0, CP0_STATUS
> .set mips3
> wait
> /* end of rollback region (the region size must be power of two) */
>
> After apply this patch. I got two error message.
> The first one is as follow
> [ 124.661211] Checking for the daddi bug... no.
> [ 124.665737] ------------[ cut here ]------------
> [ 124.670187] WARNING: at kernel/cpu/idle.c:96 cpu_startup_entry+0x150/0x178()
> [ 124.677209] Modules linked in:
> [ 124.680251] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.9.0+ #40
> [ 124.686237] Stack : 0000000000000004 0000000000000034 ffffffff80fa0000 ffffffff80292558
> 0000000000000000 ffffffff80fa0000 0000000000000001 ffffffff80293810
> 0000000000000000 0000000000000000 ffffffff81080000 ffffffff81080000
> ffffffff80e2acf0 ffffffff80f8f977 ffffffff80f8fa80 ffffffff80e31730
> 0000000000000001 0000000000000004 ffffffff00000000 0000000000000004
> ffffffffc05633f0 ffffffff806ef728 ffffffff80f57d08 ffffffff80290a74
> ffffffffc05633f0 ffffffff80293c40 000000000000003e ffffffff80e2acf0
> 0000000000000000 ffffffff80f57c30 00ffffff80f8fdc0 ffffffff802908c0
> 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> 0000000000000000 ffffffff80272498 0000000000000000 0000000000000000
> ...
> [ 124.751163] Call Trace:
> [ 124.753599] [<ffffffff80272498>] show_stack+0x68/0x80
> [ 124.758634] [<ffffffff802908c0>] warn_slowpath_common+0x78/0xa8
> [ 124.764533] [<ffffffff802d4448>] cpu_startup_entry+0x150/0x178
> [ 124.770351] [<ffffffff80fd6b04>] start_kernel+0x440/0x45c
> [ 124.775728]
> [ 124.777219] ---[ end trace 9179e654e5693e72 ]---
>
> After boot process is done the follow error message is printed periodically.
>
> [ 284.751007] INFO: rcu_preempt detected stalls on CPUs/tasks: { 6} (detected by 1, t=14712 jiffies, g=18446744073709551344, c=18446744073709551343, q=2437)
> [ 284.764878] Task dump for CPU 6:
> [ 284.768105] swapper/6 R running task 0 0 1 0x00100000
> [ 284.775174] Stack : 0000005311112000 ffffffff80f60000 ffffffff80f60000 a800000001d2d950
> 0000000000000018 ffffffff81080000 ffffffff81080000 0000000000000000
> ffffffff81010000 ffffffff8030893c 4256e5715da6083d 800000040f800000
> 0000000000000018 ffffffff81080000 ffffffff81080000 ffffffff80264f3c
> ffffffff80e31730 0000000000000000 ffffffff80e31730 ffffffff80f90000
> ffffffff80fd0000 ffffffff8026c760 0000000000000000 0000000010008ce1
> 0000000000100000 a8000000414e4010 ffffffff80f8bb18 0000000000000000
> 0000005311112000 0000000000000001 0000000000000001 0000000000000000
> ffffffff80f8bc58 a800000001d32c60 a8000000414e7fe0 0000000000008c00
> a80000003f7d8000 0000000000000000 ffffffff80fd0000 ffffffff80e31730
> ...
> [ 284.840704] Call Trace:
> [ 284.843153] [<ffffffff806f1a48>] __schedule+0x3b0/0x938
> [ 284.848377]
>
>
> Thanks
>