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932,869 commits

Author SHA1 Message Date
Jan Beulich
08ad8afaa0 x86: reduce force_mwait visibility
It's not used anywhere outside its single referencing file.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
2008-07-18 15:55:09 -07:00
Jan Beulich
08e1a13e7d x86: reduce forbid_dac's visibility
It's not used anywhere outside its declaring file.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
2008-07-18 14:39:37 -07:00
Bernhard Walle
91467bdf6e x86: move dma32_reserve_bootmem() after reserve_crashkernel()
On a x86-64 machine (nothing special I could encounter) I had the problem that
crashkernel reservation with the usual "64M@16M" failed. While debugging that,
I encountered that dma32_reserve_bootmem() reserves a memory region which is in
that area.

Because dma32_reserve_bootmem() does not rely on a specific offset but
crashkernel does, it makes sense to move the dma32_reserve_bootmem()
reservation down a bit. I tested that patch and it works without problems. I
don't see any negative effects of that move, but maybe I oversaw something ...

While we strictly don't need that patch in 2.6.27 because we have the
automatic, dynamic offset detection, it makes sense to also include it here
because:

  - it's easier to get it in -stable then,
  - many people are still used to the 'crashkernel=...@16M' syntax,
  - not everybody may be using a reloatable kernel.

Signed-off-by: Bernhard Walle <bwalle@suse.de>
Cc: kexec@lists.infradead.org
Cc: vgoyal@redhat.com
Cc: akpm@linux-foundation.org
Cc: Bernhard Walle <bwalle@suse.de>
Cc: yhlu.kernel@gmail.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 23:35:46 +02:00
Jan Beulich
369c99205f x86: fix two modpost warnings
Even though it's only the difference of the two __initdata symbols
that's being calculated, modpost still doesn't like this. So rather
calculate the size once in an __init function and store it for later
use.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
2008-07-18 14:34:08 -07:00
Jan Beulich
f2ba93929f x86: check function status in EDD boot code
Without checking the return value of get_edd_info() and adding the
entry only in the success case, 6 devices show up under
/sys/firmware/edd/, no matter how many devices are actually present.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
2008-07-18 14:33:17 -07:00
Ingo Molnar
9553e11325 Merge branch 'x86/uv' into x86/x2apic
Conflicts:

	arch/x86/kernel/Makefile

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 23:01:04 +02:00
Ingo Molnar
453c1404c5 Merge branch 'x86/apic' into x86/x2apic
Conflicts:

	arch/x86/kernel/paravirt.c
	arch/x86/kernel/smpboot.c
	arch/x86/kernel/vmi_32.c
	arch/x86/lguest/boot.c
	arch/x86/xen/enlighten.c
	include/asm-x86/apic.h
	include/asm-x86/paravirt.h

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 23:00:05 +02:00
Ingo Molnar
a208f37a46 Merge branch 'linus' into x86/x2apic 2008-07-18 22:50:34 +02:00
Ingo Molnar
0679c2f47d Merge branch 'linus' into pci-for-jesse 2008-07-18 22:39:59 +02:00
Ingo Molnar
06f8d00e9e cpumask: Optimize cpumask_of_cpu in lib/smp_processor_id.c, fix
fix typo.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 22:34:00 +02:00
Hiroshi Shimamoto
812b121d55 x86_64: ia32_signal.c: remove signal number conversion
This was old code that was needed for iBCS and x86-64 never supported that.

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 22:08:20 +02:00
Mike Travis
eb53fac5ca cpumask: Use optimized CPUMASK_ALLOC macros in the centrino_target
* Use the CPUMASK_ALLOC macros in the centrino_target() function.

Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 22:03:00 +02:00
Mike Travis
77586c2bda cpumask: Provide a generic set of CPUMASK_ALLOC macros
* Provide a generic set of CPUMASK_ALLOC macros patterned after the
    SCHED_CPUMASK_ALLOC macros.  This is used where multiple cpumask_t
    variables are declared on the stack to reduce the amount of stack
    space required.

Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 22:03:00 +02:00
Mike Travis
4755b92912 cpumask: Optimize cpumask_of_cpu in lib/smp_processor_id.c
* Optimize various places where a pointer to the cpumask_of_cpu value
    will result in reducing stack pressure.

Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 22:02:59 +02:00
Mike Travis
c18a41fbbc cpumask: Optimize cpumask_of_cpu in kernel/time/tick-common.c
* Optimize various places where a pointer to the cpumask_of_cpu value
    will result in reducing stack pressure.

Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 22:02:59 +02:00
Mike Travis
333cdd1f0e cpumask: Optimize cpumask_of_cpu in drivers/misc/sgi-xp/xpc_main.c
* Optimize various places where a pointer to the cpumask_of_cpu value
    will result in reducing stack pressure.

Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 22:02:58 +02:00
Mike Travis
c42f4f4c6d cpumask: Optimize cpumask_of_cpu in arch/x86/kernel/ldt.c
* Optimize various places where a pointer to the cpumask_of_cpu value
    will result in reducing stack pressure.

Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 22:02:58 +02:00
Mike Travis
cb6d2be60d cpumask: Optimize cpumask_of_cpu in arch/x86/kernel/io_apic_64.c
* Optimize various places where a pointer to the cpumask_of_cpu value
    will result in reducing stack pressure.

Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 22:02:57 +02:00
Mike Travis
65c0118453 cpumask: Replace cpumask_of_cpu with cpumask_of_cpu_ptr
* This patch replaces the dangerous lvalue version of cpumask_of_cpu
    with new cpumask_of_cpu_ptr macros.  These are patterned after the
    node_to_cpumask_ptr macros.

    In general terms, if there is a cpumask_of_cpu_map[] then a pointer to
    the cpumask_of_cpu_map[cpu] entry is used.  The cpumask_of_cpu_map
    is provided when there is a large NR_CPUS count, reducing
    greatly the amount of code generated and stack space used for
    cpumask_of_cpu().  The pointer to the cpumask_t value is needed for
    calling set_cpus_allowed_ptr() to reduce the amount of stack space
    needed to pass the cpumask_t value.

    If there isn't a cpumask_of_cpu_map[], then a temporary variable is
    declared and filled in with value from cpumask_of_cpu(cpu) as well as
    a pointer variable pointing to this temporary variable.  Afterwards,
    the pointer is used to reference the cpumask value.  The compiler
    will optimize out the extra dereference through the pointer as well
    as the stack space used for the pointer, resulting in identical code.

    A good example of the orthogonal usages is in net/sunrpc/svc.c:

	case SVC_POOL_PERCPU:
	{
		unsigned int cpu = m->pool_to[pidx];
		cpumask_of_cpu_ptr(cpumask, cpu);

		*oldmask = current->cpus_allowed;
		set_cpus_allowed_ptr(current, cpumask);
		return 1;
	}
	case SVC_POOL_PERNODE:
	{
		unsigned int node = m->pool_to[pidx];
		node_to_cpumask_ptr(nodecpumask, node);

		*oldmask = current->cpus_allowed;
		set_cpus_allowed_ptr(current, nodecpumask);
		return 1;
	}

Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 22:02:57 +02:00
Ingo Molnar
bb2c018b09 Merge branch 'linus' into cpus4096
Conflicts:

	drivers/acpi/processor_throttling.c

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 22:00:54 +02:00
Harvey Harrison
5108b27651 nfsd: nfs4xdr.c do-while is not a compound statement
The WRITEMEM macro produces sparse warnings of the form:
fs/nfsd/nfs4xdr.c:2668:2: warning: do-while statement is not a compound statement

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Cc: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2008-07-18 15:18:35 -04:00
Dmitry Baryshkov
9de90ac27d Sh: use generic per-device coherent dma allocator
Signed-off-by: Dmitry Baryshkov <dbaryshkov@gmail.com>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 21:14:02 +02:00
Dmitry Baryshkov
1fe532685a ARM: support generic per-device coherent dma mem
Signed-off-by: Dmitry Baryshkov <dbaryshkov@gmail.com>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 21:14:01 +02:00
Dmitry Baryshkov
538c29d43e Generic dma-coherent: fix DMA_MEMORY_EXCLUSIVE
Don't rewrite successfull allocation return values
in case the memory was marked with DMA_MEMORY_EXCLUSIVE.

Signed-off-by: Dmitry Baryshkov <dbaryshkov@gmail.com>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 21:14:01 +02:00
Ingo Molnar
f6dc8ccaab Merge branch 'linus' into core/generic-dma-coherent
Conflicts:

	kernel/Makefile

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 21:13:20 +02:00
J. Bruce Fields
ad1060c89c nfsd: Use C99 initializers in fs/nfsd/nfs4xdr.c
Thanks to problem report and original patch from Harvey Harrison.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Cc: Harvey Harrison <harvey.harrison@gmail.com>
Cc: Benny Halevy <bhalevy@panasas.com>
2008-07-18 15:04:58 -04:00
Ingo Molnar
9b610fda0d Merge branch 'linus' into timers/nohz 2008-07-18 19:53:16 +02:00
Stefan Assmann
41b9eb264c x86, pci: introduce config option for pci reroute quirks (was: [PATCH 0/3] Boot IRQ quirks for Broadcom and AMD/ATI)
This is against linux-2.6-tip, branch pci-ioapic-boot-irq-quirks.

From: Stefan Assmann <sassmann@suse.de>
Subject: Introduce config option for pci reroute quirks

The config option X86_REROUTE_FOR_BROKEN_BOOT_IRQS is introduced to
enable (or disable) the redirection of the interrupt handler to the boot
interrupt line by default. Depending on the existence of interrupt
masking / threaded interrupt handling in the kernel (vanilla, rt, ...)
and the maturity of the rerouting patch, users can enable or disable the
redirection by default.

This means that the reroute quirk can be applied to any kernel without
changing it.

Interrupt sharing could be increased if this option is enabled. However this
option is vital for threaded interrupt handling, as done by the RT kernel.
It should simplify the consolidation with the RT kernel.

The option can be overridden by either pci=ioapicreroute or
pci=noioapicreroute.

Signed-off-by: Stefan Assmann <sassmann@suse.de>
Signed-off-by: Olaf Dabrunz <od@suse.de>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: Jon Masters <jonathan@jonmasters.org>
Cc: Ihno Krumreich <ihno@suse.de>
Cc: Sven Dietrich <sdietrich@suse.de>
Cc: Daniel Gollub <dgollub@suse.de>
Cc: Felix Foerster <ffoerster@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 19:31:19 +02:00
Ingo Molnar
3e370b29d3 Merge branch 'linus' into x86/pci-ioapic-boot-irq-quirks
Conflicts:

	drivers/pci/quirks.c

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 19:31:12 +02:00
Alexander Beregalov
fa10c51a04 arch/x86/kernel/cpu/common_64.c: remove double inclusions
x86: remove double inclusions in arch/x86/kernel/cpu/common_64.c

Signed-off-by: Alexander Beregalov <a.beregalov@gmail.com>
Cc: yhlu.kernel@gmail.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 19:25:28 +02:00
Eric W. Biederman
f84dbb912f genirq: enable polling for disabled screaming irqs
When we disable a screaming irq we never see it again.  If the irq
line is shared or if the driver half works this is a real pain.  So
periodically poll the handlers for screaming interrupts.

I use a timer instead of the classic irq poll technique of working off
the timer interrupt because when we use the local apic timers
note_interrupt is never called (bug?).  Further on a system with
dynamic ticks the timer interrupt might not even fire unless there is
a timer telling it it needs to.

I forced this case on my test system with an e1000 nic and my ssh
session remained responsive despite the interrupt handler only being
called every 10th of a second.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 19:21:13 +02:00
Suresh Siddha
511d9d3418 x86: apic_ops for lguest
apic_ops for lguest.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Acked-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 19:06:13 +02:00
Suresh Siddha
9a8f0e6b5d x86: let 32bit use apic_ops too - fix
Fix VMI apic_ops.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Acked-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 19:05:29 +02:00
Hiroshi Shimamoto
1181f8b5f0 x86_32: remove redundant KERN_INFO
This printk has a KERN_ facility level in the format string.

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 19:01:04 +02:00
Steven Rostedt
1e01cb0c6f ftrace: only trace preempt off with preempt tracer
When PREEMPT_TRACER and IRQSOFF_TRACER are both configured and irqsoff
tracer is running, the preempt_off sections might also be traced.

Thanks to Andrew Morton for pointing out my mistake of spin_lock disabling
interrupts while he was reviewing ftrace.txt. Seems that my example I used
actually hit this bug.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 18:57:34 +02:00
Jaswinder Singh
6ac8d51f01 x86: introducing asm-x86/traps.h
Declaring x86 traps under one hood.
Declaring x86 do_traps before defining them.

Signed-off-by: Jaswinder Singh <jaswinder@infradead.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Alexander van Heukelum <heukelum@fastmail.fm>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 18:51:57 +02:00
Mike Travis
8df185a95c kthread: reduce stack pressure in create_kthread and kthreadd
* Replace:

  	set_cpus_allowed(..., CPU_MASK_ALL)

    with:

  	set_cpus_allowed_ptr(..., CPU_MASK_ALL_PTR)

    to remove excessive stack requirements when NR_CPUS=4096.

Signed-off-by: Mike Travis <travis@sgi.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 18:46:58 +02:00
Joerg Roedel
5ff4789d04 AMD IOMMU: set iommu for device from ACPI code too
The device<->iommu relationship has to be set from the information in the ACPI
table too. This patch adds this logic to the driver.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Cc: iommu@lists.linux-foundation.org
Cc: bhavna.sarathy@amd.com
Cc: robert.richter@amd.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 18:43:32 +02:00
Ingo Molnar
f1b0c8d3d3 Merge branch 'linus' into x86/amd-iommu 2008-07-18 18:43:08 +02:00
Thomas Petazzoni
9781f39fd2 x86: consolidate the definition of the force_mwait variable
The force_mwait variable iss defined either in
arch/x86/kernel/cpu/amd.c or in arch/x86/kernel/setup_64.c, but it is
only initialized and used in arch/x86/kernel/process.c. This patch
moves the declaration to arch/x86/kernel/process.c.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: michael@free-electrons.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 18:39:19 +02:00
Hiroshi Shimamoto
4dca10a960 softlockup: fix invalid proc_handler for softlockup_panic
The type of softlockup_panic is int, but the proc_handler is
proc_doulongvec_minmax(). This handler is for unsigned long.

This handler should be proc_dointvec_minmax().

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 18:29:28 +02:00
Alexander Beregalov
4712965422 x86 setup.c: cleanup includes
x86: remove double includes in setup.c

Signed-off-by: Alexander Beregalov <a.beregalov@gmail.com>
Cc: yhlu.kernel@gmail.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 18:21:17 +02:00
Thomas Gleixner
b8f8c3cf0a nohz: prevent tick stop outside of the idle loop
Jack Ren and Eric Miao tracked down the following long standing
problem in the NOHZ code:

	scheduler switch to idle task
	enable interrupts

Window starts here

	----> interrupt happens (does not set NEED_RESCHED)
	      	irq_exit() stops the tick

	----> interrupt happens (does set NEED_RESCHED)

	return from schedule()
	
	cpu_idle(): preempt_disable();

Window ends here

The interrupts can happen at any point inside the race window. The
first interrupt stops the tick, the second one causes the scheduler to
rerun and switch away from idle again and we end up with the tick
disabled.

The fact that it needs two interrupts where the first one does not set
NEED_RESCHED and the second one does made the bug obscure and extremly
hard to reproduce and analyse. Kudos to Jack and Eric.

Solution: Limit the NOHZ functionality to the idle loop to make sure
that we can not run into such a situation ever again.

cpu_idle()
{
	preempt_disable();

	while(1) {
		 tick_nohz_stop_sched_tick(1); <- tell NOHZ code that we
		 			          are in the idle loop

		 while (!need_resched())
		       halt();

		 tick_nohz_restart_sched_tick(); <- disables NOHZ mode
		 preempt_enable_no_resched();
		 schedule();
		 preempt_disable();
	}
}

In hindsight we should have done this forever, but ... 

/me grabs a large brown paperbag.

Debugged-by: Jack Ren <jack.ren@marvell.com>, 
Debugged-by: eric miao <eric.y.miao@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-07-18 18:10:28 +02:00
Herton Ronaldo Krzesinski
723edb5060 Fix typos from signal_32/64.h merge
Fallout from commit 33185c504f ("x86:
merge signal_32/64.h")

Thanks to Dick Streefland who provided an useful testcase on
http://lkml.org/lkml/2008/3/17/205 (only applicable to 2.6.24.x), that
helped a lot as a deterministic way to bisect an issue that leaded to
this fix.

Signed-off-by: Herton Ronaldo Krzesinski <herton@mandriva.com.br>
Signed-off-by: Luiz Fernando N. Capitulino <lcapitulino@mandriva.com.br>
Cc: Roland McGrath <roland@redhat.com>
Cc: <stable@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 17:59:13 +02:00
Akinobu Mita
8b2b9c1af0 x86, intel_cacheinfo: fix use-after-free cache_kobject
This avoids calling kobject_uevent() with cache_kobject that has
already been deallocated in an error path.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 17:49:33 +02:00
Ingo Molnar
3f9b5cc018 x86: re-enable OPTIMIZE_INLINING
re-enable OPTIMIZE_INLINING more widely. Jeff Dike fixed the remaining
outstanding issue in this commit:

| commit 4f81c5350b
| Author: Jeff Dike <jdike@addtoit.com>
| Date:   Mon Jul 7 13:36:56 2008 -0400
|
|     [UML] fix gcc ICEs and unresolved externs
[...]
|    This patch reintroduces unit-at-a-time for gcc >= 4.0, bringing back the
|    possibility of Uli's crash.  If that happens, we'll debug it.

it's still default-off and thus opt-in.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 16:30:05 +02:00
Alexander van Heukelum
7dedcee394 x86: traps_xx: modify x86_64 to use _log_lvl variants
i386 has show_trace_log_lvl and show_stack_log_lvl, allowing
traces to be emitted with log-level annotations. This patch
introduces them to x86_64, but log_lvl is only ever set to
an empty string. Output of traces is unchanged.

i386-chunk is whitespace-only.

Signed-off-by: Alexander van Heukelum <heukelum@fastmail.fm>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 16:21:17 +02:00
Alexander van Heukelum
78cbac65fd x86: traps_xx: refactor die() like in x86_64
Make the diff between the traps_32.c and traps_64.c a bit smaller.

Change traps_32.c to look more like traps_64.c:
 - move lock information to file scope
 - split out oops_begin() and oops_end() from die()
 - increment nest counter in oops_begin

Only whitespace change in traps_64.c

No functional changes intended.

Signed-off-by: Alexander van Heukelum <heukelum@fastmail.fm>
Acked-by: Cyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 16:21:17 +02:00
Lai Jiangshan
5127bed588 rcu classic: new algorithm for callbacks-processing(v2)
This is v2, it's a little deference from v1 that I
had send to lkml.
use ACCESS_ONCE
use rcu_batch_after/rcu_batch_before for batch # comparison.

rcutorture test result:
(hotplugs: do cpu-online/offline once per second)

No CONFIG_NO_HZ:           OK, 12hours
No CONFIG_NO_HZ, hotplugs: OK, 12hours
CONFIG_NO_HZ=y:            OK, 24hours
CONFIG_NO_HZ=y, hotplugs:  Failed.
(Failed also without my patch applied, exactly the same bug occurred,
http://lkml.org/lkml/2008/7/3/24)

v1's email thread:
http://lkml.org/lkml/2008/6/2/539

v1's description:

The code/algorithm of the implement of current callbacks-processing
is very efficient and technical. But when I studied it and I found
a disadvantage:

In multi-CPU systems, when a new RCU callback is being
queued(call_rcu[_bh]), this callback will be invoked after the grace
period for the batch with batch number = rcp->cur+2 has completed
very very likely in current implement. Actually, this callback can be
invoked after the grace period for the batch with
batch number = rcp->cur+1 has completed. The delay of invocation means
that latency of synchronize_rcu() is extended. But more important thing
is that the callbacks usually free memory, and these works are delayed
too! it's necessary for reclaimer to free memory as soon as
possible when left memory is few.

A very simple way can solve this problem:
a field(struct rcu_head::batch) is added to record the batch number for
the RCU callback. And when a new RCU callback is being queued, we
determine the batch number for this callback(head->batch = rcp->cur+1)
and we move this callback to rdp->donelist if we find
that head->batch <= rcp->completed when we process callbacks.
This simple way reduces the wait time for invocation a lot. (about
2.5Grace Period -> 1.5Grace Period in average in multi-CPU systems)

This is my algorithm. But I do not add any field for struct rcu_head
in my implement. We just need to memorize the last 2 batches and
their batch number, because these 2 batches include all entries that
for whom the grace period hasn't completed. So we use a special
linked-list rather than add a field.
Please see the comment of struct rcu_data.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Dipankar Sarma <dipankar@in.ibm.com>
Cc: Gautham Shenoy <ego@in.ibm.com>
Cc: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 16:07:33 +02:00
Lai Jiangshan
3cac97cbb1 rcu classic: simplify the next pending batch
use a batch number(rcp->pending) instead of a flag(rcp->next_pending)

rcu_start_batch() need to change this flag, so mb()s is needed
for memory-access safe.

but(after this patch applied) rcu_start_batch() do not change
this batch number(rcp->pending), rcp->pending is managed by
__rcu_process_callbacks only, and troublesome mb()s are eliminated.

And codes look simpler and clearer.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Dipankar Sarma <dipankar@in.ibm.com>
Cc: Gautham Shenoy <ego@in.ibm.com>
Cc: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 16:07:32 +02:00