Re: [PATCH] [16/48] Suspend2 2.1.9.8 for 2.6.12: 406-dynamic-pageflags.patch

[Shaohua Li <shaohua.li@intel.com>]

On Wed, 2005-07-06 at 12:20 +1000, Nigel Cunningham wrote:
> +
> +/*
> + * Save and restore processor state for secondary processors.
> + * IRQs (and therefore preemption) are already disabled 
> + * when we enter here (IPI).
> + */
> +
> +static volatile int loop __nosavedata;
> +
> +void __smp_suspend_lowlevel(void * data)
> +{
> +	__asm__( "movl %%ecx,%%cr3\n" ::"c"(__pa(swsusp_pg_dir)));
> +
> +	if (test_suspend_state(SUSPEND_NOW_RESUMING)) {
> +		BUG_ON(!irqs_disabled());
> +		kernel_fpu_begin();
> +		c_loops_per_jiffy_ref[_smp_processor_id()] = current_cpu_data.loops_per_jiffy;
> +		atomic_inc(&suspend_cpu_counter);
> +
> +		/* Only image copied back while we spin in this loop. Our
> +		 * task info should not be looked at while this is happening
> +		 * (which smp_processor_id() will do( */
> +		while (test_suspend_state(SUSPEND_FREEZE_SMP)) { 
> +			cpu_relax();
> +			barrier();
> +		}
> +
> +		while (atomic_read(&suspend_cpu_counter) != _smp_processor_id()) {
> +			cpu_relax();
> +			barrier();
> +		}
> +	       	my_saved_context = (unsigned char *) (suspend2_saved_contexts + _smp_processor_id());
> +		for (loop = sizeof(struct suspend2_saved_context); loop--; loop)
> +			*(((unsigned char *) &suspend2_saved_context) + loop - 1) = *(my_saved_context + loop - 1);
> +		suspend2_restore_processor_context();
> +		cpu_clear(_smp_processor_id(), per_cpu(cpu_tlbstate, _smp_processor_id()).active_mm->cpu_vm_mask);
> +		load_cr3(swapper_pg_dir);
> +		wbinvd();
> +		__flush_tlb_all();
> +		current_cpu_data.loops_per_jiffy = c_loops_per_jiffy_ref[_smp_processor_id()];
> +		mtrr_restore_one_cpu();
> +		atomic_dec(&suspend_cpu_counter);
> +	} else {	/* suspending */
> +		BUG_ON(!irqs_disabled());
> +		/* 
> +		 *Save context and go back to idling.
> +		 * Note that we cannot leave the processor
> +		 * here. It must be able to receive IPIs if
> +		 * the LZF compression driver (eg) does a
> +		 * vfree after compressing the kernel etc
> +		 */
> +		while (test_suspend_state(SUSPEND_FREEZE_SMP) &&
> +			(atomic_read(&suspend_cpu_counter) != (_smp_processor_id() - 1))) {
> +			cpu_relax();
> +			barrier();
> +		}
> +		suspend2_save_processor_context();
> +		my_saved_context = (unsigned char *) (suspend2_saved_contexts + _smp_processor_id());
> +		for (loop = sizeof(struct suspend2_saved_context); loop--; loop)
> +			*(my_saved_context + loop - 1) = *(((unsigned char *) &suspend2_saved_context) + loop - 1);
> +		atomic_inc(&suspend_cpu_counter);
> +		/* Now spin until the atomic copy of the kernel is made. */
> +		while (test_suspend_state(SUSPEND_FREEZE_SMP)) {
> +			cpu_relax();
> +			barrier();
> +		}
> +		atomic_dec(&suspend_cpu_counter);
> +		kernel_fpu_end();
> +	}
> +}
we are using cpu hotplug for S3 & S4 SMP to avoid nasty deadlocks. Could
this be avoided in suspend2 SMP?

Thanks,
Shaohua