cpu_init is called during resume

cpu_init is called during resume

[Pavel Machek]

cpu_init() is called during resume, at time when GFP_KERNEL is not
available. This silences warning, and adds few small cleanups.

Signed-off-by: Pavel Machek <pavel@suse.cz>

---
commit 0c23b1939d38a6bbdf1fd22078bd4fd3ec932c68
tree 66e19bcca9940e3cab2df78aaef010e51260cb9f
parent de9ee8a9c1e2cf18adee5d1569daa19deedc7c87
author <pavel@amd.ucw.cz> Thu, 31 Aug 2006 15:55:00 +0200
committer <pavel@amd.ucw.cz> Thu, 31 Aug 2006 15:55:00 +0200

 arch/i386/kernel/cpu/common.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/i386/kernel/cpu/common.c b/arch/i386/kernel/cpu/common.c
index 70c87de..d0565d3 100644
--- a/arch/i386/kernel/cpu/common.c
+++ b/arch/i386/kernel/cpu/common.c
@@ -591,10 +591,10 @@ void __init early_cpu_init(void)
 void __cpuinit cpu_init(void)
 {
 	int cpu = smp_processor_id();
-	struct tss_struct * t = &per_cpu(init_tss, cpu);
+	struct tss_struct *t = &per_cpu(init_tss, cpu);
 	struct thread_struct *thread = &current->thread;
 	struct desc_struct *gdt;
-	__u32 stk16_off = (__u32)&per_cpu(cpu_16bit_stack, cpu);
+	u32 stk16_off = (u32)&per_cpu(cpu_16bit_stack, cpu);
 	struct Xgt_desc_struct *cpu_gdt_descr = &per_cpu(cpu_gdt_descr, cpu);
 
 	if (cpu_test_and_set(cpu, cpu_initialized)) {
@@ -629,7 +629,7 @@ void __cpuinit cpu_init(void)
 		/* alloc_bootmem_pages panics on failure, so no check */
 		memset(gdt, 0, PAGE_SIZE);
 	} else {
-		gdt = (struct desc_struct *)get_zeroed_page(GFP_KERNEL);
+		gdt = (struct desc_struct *)get_zeroed_page(GFP_ATOMIC);
 		if (unlikely(!gdt)) {
 			printk(KERN_CRIT "CPU%d failed to allocate GDT\n", cpu);
 			for (;;)

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: cpu_init is called during resume

[Jeremy Fitzhardinge]

Pavel Machek wrote:
> cpu_init() is called during resume, at time when GFP_KERNEL is not
> available. This silences warning, and adds few small cleanups.
>   

I presume this is resume from disk.  If you're doing resume from RAM, 
all the CPU-related stuff should already be allocated, unless you're 
bringing up a new CPU which wasn't previously there, right?

What's the call path for this on resume?  In my i386-pda patches, I've 
rearranged this so that the secondary CPU's GDT (and PDA) are 
pre-allocated on the boot CPU.  Does this help this case, or would they 
still need to be atomic allocations?

And wouldn't making these allocations atomic make real CPU hotplug (ie, 
on an active, running system) more likely to fail?  This code doesn't 
deal with allocation failure very elegantly.

    J

Re: cpu_init is called during resume

[Pavel Machek]

Hi!

> >cpu_init() is called during resume, at time when GFP_KERNEL is not
> >available. This silences warning, and adds few small cleanups.
> >  
> 
> I presume this is resume from disk.  If you're doing resume from RAM, 
> all the CPU-related stuff should already be allocated, unless you're 
> bringing up a new CPU which wasn't previously there, right?

We are doing virtual cpu hotplug/unplug... actually suspend to RAM
*and* disk. Just try it :-).

> And wouldn't making these allocations atomic make real CPU hotplug (ie, 
> on an active, running system) more likely to fail?  This code doesn't 
> deal with allocation failure very elegantly.

Hmm... well hopefully free_pages_min will cover this case.
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: cpu_init is called during resume

[Jeremy Fitzhardinge]

Pavel Machek wrote:
> We are doing virtual cpu hotplug/unplug... actually suspend to RAM
> *and* disk. Just try it :-).
>   

Yes, I know, but if you're replugging a CPU it should already have a GDT 
allocated, so the kmalloc() won't be called in the resume case.  So if 
there's a problem, it can only be on the resume-from-disk path, on the 
assumption that that secondary CPU hasn't already been brought up.

    J

Re: cpu_init is called during resume

[Pavel Machek]

On Thu 2006-08-31 16:52:42, Jeremy Fitzhardinge wrote:
> Pavel Machek wrote:
> >We are doing virtual cpu hotplug/unplug... actually suspend to RAM
> >*and* disk. Just try it :-).
> >  
> 
> Yes, I know, but if you're replugging a CPU it should already have a GDT 
> allocated, so the kmalloc() won't be called in the resume case.  So if 
> there's a problem, it can only be on the resume-from-disk path, on the 
> assumption that that secondary CPU hasn't already been brought up.

I think gdt is destroyed on cpu unplug, no? I guess I'll have to redo
my testing...

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

-- 
VGER BF report: H 0.410571

Re: cpu_init is called during resume

[Jeremy Fitzhardinge]

Pavel Machek wrote:
> I think gdt is destroyed on cpu unplug, no? I guess I'll have to redo
> my testing...
>   

No, I don't think it is.  arch/i386/cpu/common.c:cpu_uninit() doesn't 
free anything.

    J

-- 
VGER BF report: H 0