Subject: Re: [PATCH] 2 of 3 kdump-ppc64-soft-reset-fixes

From: Andrew Morton <[email-masked]>
Date: Mon, 10 Apr 2006 15:58:38 -0700

David Wilder <[email-masked]> wrote:

Please don't use a filename as a patch title.  See section 2 of
http://www.zip.com.au/~akpm/linux/patches/stuff/tpp.txt.

> --- 2617-rc1.orig/arch/powerpc/kernel/crash.c	2006-04-05 13:20:38.000000000 -0700
> +++ 2617-rc1/arch/powerpc/kernel/crash.c	2006-04-05 13:24:19.000000000 -0700
> @@ -23,6 +23,7 @@
>  #include <linux/elfcore.h>
>  #include <linux/init.h>
>  #include <linux/types.h>
> +#include <linux/irq.h>
>  
>  #include <asm/processor.h>
>  #include <asm/machdep.h>
> @@ -40,6 +41,9 @@
>  
>  /* This keeps a track of which one is crashing cpu. */
>  int crashing_cpu = -1;
> +static cpumask_t cpus_in_crash = CPU_MASK_NONE;
> +extern struct kimage *kexec_crash_image;
> +extern cpumask_t cpus_in_sr;

extern declarations should be placed in .h, not in .c.

> +	while (!cpu_isset(crashing_cpu, cpus_in_crash)) 
> +		barrier();

The patch contains lots of busy-loops which all do barrier().

barrier() is purely a compiler thing.  I suspect you meant cpu_relax(). 
Either way, there should be a cpu_relax() in these loops.

> +
> +/*
> + * This function will be called by secondary cpus or by kexec cpu 
> + * if soft-reset is activated to stop some CPUs.
> + */
> +void crash_kexec_secondary(struct pt_regs *regs)
> +{
> +	int cpu = smp_processor_id();
> +	unsigned long flags;
> +	int msecs = 5;
> +
> +	local_irq_save(flags);
> +	/* Wait 5ms if the kexec CPU is not entered yet. */
> +	while (crashing_cpu < 0) {
> +		if (--msecs < 0) {
> +			/*
> +			 * Either kdump image is not loaded or
> +			 * kdump process is not started - Probably xmon
> +			 * exited using 'x'(exit and recover) or 
> +			 * kexec_should_crash() failed for all running tasks.
> +			 */
> +			cpu_clear(cpu, cpus_in_sr);
> +			local_irq_restore(flags);
> +			return;
> +		}
> +		mdelay(1);
> +		barrier();
> +	}
> +        if (cpu == crashing_cpu) {

Whitespace broke here.

> +		/*
> +		 * Panic CPU will enter this func only via soft-reset.
> +		 * Wait until all secondary CPUs entered and
> +		 * then start kexec boot.
> +		 */
> +		crash_soft_reset_check(cpu);
> +		cpu_set(crashing_cpu, cpus_in_crash);
> +		if (ppc_md.kexec_cpu_down)
> +			ppc_md.kexec_cpu_down(1, 0);
> +		machine_kexec(kexec_crash_image);
> +		/* NOTREACHED */
> +	}
> +	crash_ipi_callback(regs);
> +}