Date:	Sun, 18 Mar 2007 01:00:01 +0200
From:	Maxim <maximlevitsky@...il.com>
To:	Len Brown <lenb@...nel.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [BUG] 2.6.21-rc1,2,3 regressions on my system that I found so far

On Saturday 17 March 2007 01:19:44 Len Brown wrote:
> On Friday 16 March 2007 06:30, Maxim Levitsky wrote:
> > 
> > Good day, 
> > 
> > I want to report regressions I have with 2.6.21-rc3 kernel.
> > I use CONFIG_NO_HZ.
> 
> Do any of these issues go away with CONFIG_NO_HZ=n (or boot with nohz=n)
> or are they all independent of it?
> 
> thanks,
> -Len
> 
> > 1) Both suspend to disk and suspend to RAM are completely broken:
> > On vanilla 2.6.20 suspend to disk works perfectly and suspend to ram works _almost_ perfectly (I will tell about that later).
> > On 2.6.21-rc1 and later system hangs even before suspend begins (suspend to disk hangs before image write , and after suspend to ram , 
> > some devices are powered down (disk,power leds) , and some and not(fans, power) , and system hangs).
> > 
> > I did a git-bisect and I found which commit caused that:
> > 	e3c7db621bed4afb8e231cb005057f2feb5db557 - [PATCH] [PATCH] PM: Change code ordering in main.c (breaks  S3)
> > 	ed746e3b18f4df18afa3763155972c5835f284c5 - [PATCH] [PATCH] swsusp: Change code ordering in disk.c (breaks swsusp, I don't use it, but I tested it)
> >         259130526c267550bc365d3015917d90667732f1 - [PATCH] [PATCH] swsusp: Change code ordering in user.c (breaks uswsusp, that I use)
> > 
> > I reverted those commits and now system suspends correctly to disk, but suspend to ram showed some more regressions.
> > 
> > 
> > 2) ) After suspend to ram I get this 
> > 
> > Mar 14 00:22:23 MAIN kernel: [    2.072875] caller is check_tsc_sync_source+0x1d/0x100
> > Mar 14 00:22:23 MAIN kernel: [    2.072878]  [show_trace_log_lvl+26/48] show_trace_log_lvl+0x1a/0x30
> > Mar 14 00:22:23 MAIN kernel: [    2.072881]  [show_trace+18/32] show_trace+0x12/0x20
> > Mar 14 00:22:23 MAIN kernel: [    2.072884]  [dump_stack+22/32] dump_stack+0x16/0x20
> > Mar 14 00:22:23 MAIN kernel: [    2.072887]  [debug_smp_processor_id+173/176] debug_smp_processor_id+0xad/0xb0
> > Mar 14 00:22:23 MAIN kernel: [    2.072891]  [check_tsc_sync_source+29/256] check_tsc_sync_source+0x1d/0x100
> > Mar 14 00:22:23 MAIN kernel: [    2.072894]  [__cpu_up+80/384] __cpu_up+0x50/0x180
> > Mar 14 00:22:23 MAIN kernel: [    2.072897]  [_cpu_up+98/208] _cpu_up+0x62/0xd0
> > Mar 14 00:22:23 MAIN kernel: [    2.072901]  [cpu_up+46/80] cpu_up+0x2e/0x50
> > Mar 14 00:22:23 MAIN kernel: [    2.072903]  [enable_nonboot_cpus+110/160] enable_nonboot_cpus+0x6e/0xa0
> > Mar 14 00:22:23 MAIN kernel: [    2.072906]  [enter_state+326/496] enter_state+0x146/0x1f0
> > Mar 14 00:22:23 MAIN kernel: [    2.072909]  [state_store+174/192] state_store+0xae/0xc0
> > Mar 14 00:22:23 MAIN kernel: [    2.072912]  [subsys_attr_store+43/64] subsys_attr_store+0x2b/0x40
> > Mar 14 00:22:23 MAIN kernel: [    2.072917]  [sysfs_write_file+186/272] sysfs_write_file+0xba/0x110
> > Mar 14 00:22:23 MAIN kernel: [    2.072920]  [vfs_write+150/352] vfs_write+0x96/0x160
> > Mar 14 00:22:23 MAIN kernel: [    2.072923]  [sys_write+61/112] sys_write+0x3d/0x70
> > Mar 14 00:22:23 MAIN kernel: [    2.072926]  [sysenter_past_esp+93/153] sysenter_past_esp+0x5d/0x99
> > Mar 14 00:22:23 MAIN kernel: [    2.072929]  =======================
> > Mar 14 00:22:23 MAIN kernel: [    2.072931] checking TSC synchronization [CPU#0 -> CPU#1]:
> > Mar 14 00:22:23 MAIN kernel: [    2.092922] Measured 72051818872 cycles TSC warp between CPUs, turning off
> > 
> > It looks clear that preempt is enabled all the way in second cpu initialization, ( I think that at least in check_tsc_sync_source, it should be disabled,
> > shouldn't it ? )
> > 
> > Then I did add preempt_disable() / preempt_enable()  to this function , and  I still got this:
> > 
> > Mar 14 00:22:23 MAIN kernel: [    2.072931] checking TSC synchronization [CPU#0 -> CPU#1]:
> > Mar 14 00:22:23 MAIN kernel: [    2.092922] Measured 72051818872 cycles TSC warp between CPUs, turning off
> > 
> > It happens after second CPU is brought back on-line.
> > 
> > Now I understand that this is TSC sync problem and I tried to do some tests:
> > 
> >  I tried to disable/enable second CPU by hand, eg I did number of times,
> > 
> > echo "0" > /sys/devices/system/cpu/cpu1/online
> > echo "1" > /sys/devices/system/cpu/cpu1/online
> > 
> > and TSC sync was ok.
> > 
> > Then I disabled 2nd CPU, have suspended system to RAM , resumed it  , and then enabled 2nd CPU and got same error message.
> > Then I disabled cpufreq , and did above tests, and got same results.
> > I think that maybe this error is false, that there is some difference in TSC clock, but this difference is constant, and can be fixed
> > 
> > 3) Sometimes I get this (once in three boots or so)
> > 
> > [   36.217405] ENABLING IO-APIC IRQs
> > [   36.217587] ..TIMER: vector=0x31 apic1=0 pin1=2 apic2=-1 pin2=-1
> > [   36.433917] APIC timer disabled due to verification failure.
> > 
> > And NO_HZ is disabled due to that (I get 1000/s timer's interrupts)
> > I haven't investigated that yet.
> > It looks like another new test that my hardware fails to perform... 
> > 
> > 
> > And now I want to tell you about that _almost_ working suspend to ram I got in 2.6.20:
> > To put it simply sometimes system wakes from resume, and sometimes not (about 1 in 5 times)
> > When it does it works perfectly. 
> > 
> > This is quite common problem but ironically my case is very different and harder to solve.
> > 
> > The fact is that I found thanks to RTC tricks , similar to PM_TRACE that system hangs in exactly three places (in one of them of course)
> > 
> > I put between instructions, code like that to save a position in RTC alarm which is not cleared on reboot
> > Note that this code uses ax, but I checked every time I put it that ax can be used (eg, it is loaded in next instruction)
> > 
> > #define TRACE(val) 			 \
> > 	movb	$0x01, %al		; \
> > 	outb	%al, $0x70 		; \
> > 	movb	$ ## val, %al 		; \
> > 	outb	%al, $0x71
> > 
> > It hangs very early in asm code, and those are places:
> > 
> > 1) /home/maxim/software/kernel/linux-2.6.20-mod/arch/i386/kernel/acpi/wakeup.S:wakeup_start:
> > 	ljmpl	$__KERNEL_CS,$wakeup_pmode_return
> > As I see that is first time wakeup low page is addressing kernel memory by jumping to it.
> > 
> > 2)  /home/maxim/software/kernel/linux-2.6.20-mod/arch/i386/kernel/acpi/wakeup.S:do_suspend_lowlevel
> > 	call	restore_registers 
> > It hangs exacly on that instruction, I can only see that this is first time protected stack is accessed
> > 
> > 3) /home/maxim/software/kernel/linux-2.6.20-mod/arch/i386/power/cpu.c :__restore_processor_state(struct saved_context *ctxt)
> > 	mtrr_ap_init();
> > 
> > It hangs somewhere inside this function, and because is is long I haven't found where exactly, it is easier to disable MTRR all together.
> > 
> > Note that all three places have different external behavier:
> > 
> > in first case, system powers on -> off -> on -> hangs
> > I did put test in RTC to see whenever BIOS call kernel twice but I know from this test for sure that it calls it only once,
> > It actualy makes sense, because exception occures before IDT is loaded, so system has no choice but to power down
> > 
> > in second case I see blinking leds -> almost sure a oops
> > 
> > in third case system just hangs
> > 
> > That's all, I will continue to dig those problems out
> > 
> > Thanks for attention,
> > 	Maxim Levitsky
> > -
> > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
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> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at  http://www.tux.org/lkml/
> > 
> 

Issues that are caused by those

        e3c7db621bed4afb8e231cb005057f2feb5db557 - [PATCH] [PATCH] PM: Change code ordering in main.c (breaks  S3)
        ed746e3b18f4df18afa3763155972c5835f284c5 - [PATCH] [PATCH] swsusp: Change code ordering in disk.c (breaks swsusp, I don't use it, but I tested it)
        259130526c267550bc365d3015917d90667732f1 - [PATCH] [PATCH] swsusp: Change code ordering in user.c (breaks uswsusp, that I use)

doesn't go away, even worse, I tested latest Linus's git tree, and same hang both is suspend to disk and suspend to ram (before suspending)



>Mar 14 00:22:23 MAIN kernel: [    2.072875] caller is check_tsc_sync_source+0x1d/0x100
>Mar 14 00:22:23 MAIN kernel: [    2.072878]  [show_trace_log_lvl+26/48] show_trace_log_lvl+0x1a/0x30
>Mar 14 00:22:23 MAIN kernel: [    2.072881]  [show_trace+18/32] show_trace+0x12/0x20
>Mar 14 00:22:23 MAIN kernel: [    2.072884]  [dump_stack+22/32] dump_stack+0x16/0x20
>Mar 14 00:22:23 MAIN kernel: [    2.072887]  [debug_smp_processor_id+173/176] debug_smp_processor_id+0xad/0x


^ This thing is fixed (sorry for bothering you)


>Mar 14 00:22:23 MAIN kernel: [    2.072931] checking TSC synchronization [CPU#0 -> CPU#1]:
>Mar 14 00:22:23 MAIN kernel: [    2.092922] Measured 72051818872 cycles TSC warp between CPUs, turning off

^ This one I don't think is related to NO_HZ, maybe it is hardware problem, but it exist without NO_HZ


>[   36.217405] ENABLING IO-APIC IRQs
>[   36.217587] ..TIMER: vector=0x31 apic1=0 pin1=2 apic2=-1 pin2=-1
>[   36.433917] APIC timer disabled due to verification failure.

This one is now discussed, I will look at it and it is not related to NO_HZ

And hangs with S3 as I said occur even in 2.6.20


And I forgot to tell about another problem with (now I know ,hi-resolution timers)
That before suspend to ram APIC timer is used and HPET is not used :

root@...N:/home/maxim# cat /sys/devices/system/clockevents/clockevents0/registered
lapic                F:0007 M:3(periodic) C: 1
hpet                 F:0003 M:1(shutdown) C: 0
lapic                F:0007 M:3(periodic) C: 0
root@...N:/home/maxim#   


But after suspend to ram HPET is 'woken'

root@...N:/home/maxim# cat /sys/devices/system/clockevents/clockevents0/registered
lapic                F:0007 M:3(one shoot) C: 1
hpet                 F:0003 M:3(one shoot) C: 0
lapic                F:0007 M:3(one shoot) C: 0

Note that I added those (one shoot), (periodic) descriptions, would be nice to have them in kernel, can I send a patch ?  ;-)

and I see average of 18 IRQs/sec on IRQ 0


Best regards,
	Maxim Levitsky

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