| Commit message (Collapse) | Author | Age | Files | Lines |
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git://git.kernel.org/pub/scm/linux/kernel/git/adobriyan/proc
* 'proc' of git://git.kernel.org/pub/scm/linux/kernel/git/adobriyan/proc:
proc: remove kernel.maps_protect
proc: remove now unneeded ADDBUF macro
[PATCH] proc: show personality via /proc/pid/personality
[PATCH] signal, procfs: some lock_task_sighand() users do not need rcu_read_lock()
proc: move PROC_PAGE_MONITOR to fs/proc/Kconfig
proc: make grab_header() static
proc: remove unused get_dma_list()
proc: remove dummy vmcore_open()
proc: proc_sys_root tweak
proc: fix return value of proc_reg_open() in "too late" case
Fixed up trivial conflict in removed file arch/sparc/include/asm/dma_32.h
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After commit 831830b5a2b5d413407adf380ef62fe17d6fcbf2 aka
"restrict reading from /proc/<pid>/maps to those who share ->mm or can ptrace"
sysctl stopped being relevant because commit moved security checks from ->show
time to ->start time (mm_for_maps()).
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Acked-by: Kees Cook <kees.cook@canonical.com>
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rcu_read_lock()
lock_task_sighand() make sure task->sighand is being protected,
so we do not need rcu_read_lock().
[ exec() will get task->sighand->siglock before change task->sighand! ]
But code using rcu_read_lock() _just_ to protect lock_task_sighand()
only appear in procfs. (and some code in procfs use lock_task_sighand()
without such redundant protection.)
Other subsystem may put lock_task_sighand() into rcu_read_lock()
critical region, but these rcu_read_lock() are used for protecting
"for_each_process()", "find_task_by_vpid()" etc. , not for protecting
lock_task_sighand().
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
[ok from Oleg]
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
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Various people outside the tty layer still stick their noses in behind the
scenes. We need to make sure they also obey the locking and referencing rules.
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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This is pure tty code so put it in the tty layer where it can be with the
locking relevant material it uses
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Introduce a kref to the tty structure and use it to protect the tty->signal
tty references. For now we don't introduce it for anything else.
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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master.kernel.org:/pub/scm/linux/kernel/git/torvalds/linux-2.6
Conflicts:
sound/core/memalloc.c
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'x86-v28-for-linus-phase4-D' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (186 commits)
x86, debug: print more information about unknown CPUs
x86 setup: handle more than 8 CPU flag words
x86: cpuid, fix typo
x86: move transmeta cap read to early_init_transmeta()
x86: identify_cpu_without_cpuid v2
x86: extended "flags" to show virtualization HW feature in /proc/cpuinfo
x86: move VMX MSRs to msr-index.h
x86: centaur_64.c remove duplicated setting of CONSTANT_TSC
x86: intel.c put workaround for old cpus together
x86: let intel 64-bit use intel.c
x86: make intel_64.c the same as intel.c
x86: make intel.c have 64-bit support code
x86: little clean up of intel.c/intel_64.c
x86: make 64 bit to use amd.c
x86: make amd_64 have 32 bit code
x86: make amd.c have 64bit support code
x86: merge header in amd_64.c
x86: add srat_detect_node for amd64
x86: remove duplicated force_mwait
x86: cpu make amd.c more like amd_64.c v2
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Conflicts:
arch/x86/kernel/cpu/common.c
arch/x86/kernel/signal_64.c
include/asm-x86/cpufeature.h
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Conflicts:
arch/x86/kernel/cpu/amd.c
arch/x86/kernel/cpu/common.c
arch/x86/kernel/cpu/common_64.c
arch/x86/kernel/cpu/feature_names.c
include/asm-x86/cpufeature.h
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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add reserve_region_with_split() to not lose e820 reserved entries if
they overlap with existing IO regions:
with test case by extend 0xe0000000 - 0xeffffff to 0xdd800000 -
we get:
e0000000-efffffff : PCI MMCONFIG 0
e0000000-efffffff : reserved
and in /proc/iomem we get:
found conflict for reserved [dd800000, efffffff], try to reserve with split
__reserve_region_with_split: (PCI Bus #80) [dd000000, ddffffff], res: (reserved) [dd800000, efffffff]
__reserve_region_with_split: (PCI Bus #00) [de000000, dfffffff], res: (reserved) [de000000, efffffff]
initcall pci_subsys_init+0x0/0x121 returned 0 after 381 msecs
in dmesg
various fixes and improvements suggested by Linus.
Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Conflicts:
arch/x86/kernel/cpu/feature_names.c
include/asm-x86/cpufeature.h
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Conflicts:
arch/x86/kernel/apic_32.c
arch/x86/kernel/apic_64.c
arch/x86/kernel/setup.c
drivers/pci/intel-iommu.c
include/asm-x86/cpufeature.h
include/asm-x86/dma-mapping.h
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Conflicts:
arch/x86/kernel/genapic_64.c
include/asm-x86/kvm_host.h
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Conflicts:
include/asm-x86/dma-mapping.h
include/asm-x86/namei.h
include/asm-x86/uaccess.h
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Conflicts:
include/asm-x86/i8259.h
include/asm-x86/msidef.h
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Conflicts:
drivers/pci/dmar.c
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Generic infrastructure for migrating the irq from the process context in the
presence of CONFIG_GENERIC_PENDING_IRQ.
This will be used later for migrating irq in the presence of
interrupt-remapping.
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: akpm@linux-foundation.org
Cc: arjan@linux.intel.com
Cc: andi@firstfloor.org
Cc: ebiederm@xmission.com
Cc: jbarnes@virtuousgeek.org
Cc: steiner@sgi.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'x86-v28-for-linus-phase3-B' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (74 commits)
AMD IOMMU: use iommu_device_max_index, fix
AMD IOMMU: use iommu_device_max_index
x86: add PCI IDs for AMD Barcelona PCI devices
x86/iommu: use __GFP_ZERO instead of memset for GART
x86/iommu: convert GART need_flush to bool
x86/iommu: make GART driver checkpatch clean
x86 gart: remove unnecessary initialization
x86: restore old GART alloc_coherent behavior
revert "x86: make GART to respect device's dma_mask about virtual mappings"
x86: export pci-nommu's alloc_coherent
iommu: remove fullflush and nofullflush in IOMMU generic option
x86: remove set_bit_string()
iommu: export iommu_area_reserve helper function
AMD IOMMU: use coherent_dma_mask in alloc_coherent
add AMD IOMMU tree to MAINTAINERS file
AMD IOMMU: use cmd_buf_size when freeing the command buffer
AMD IOMMU: calculate IVHD size with a function
AMD IOMMU: remove unnecessary cast to u64 in the init code
AMD IOMMU: free domain bitmap with its allocation order
AMD IOMMU: simplify dma_mask_to_pages
...
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x86-v28-for-linus-phase3-B
Conflicts:
arch/x86/kernel/pci-gart_64.c
include/asm-x86/dma-mapping.h
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Conflicts:
lib/swiotlb.c
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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fixes modular builds:
ERROR: "dma_alloc_from_coherent" [sound/core/snd-page-alloc.ko] undefined!
ERROR: "dma_release_from_coherent" [sound/core/snd-page-alloc.ko] undefined!
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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git://git.kernel.org/pub/scm/linux/kernel/git/davej/cpufreq
* 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/davej/cpufreq:
[CPUFREQ] Fix BUG: using smp_processor_id() in preemptible code
[CPUFREQ] Don't export governors for default governor
[CPUFREQ][6/6] cpufreq: Add idle microaccounting in ondemand governor
[CPUFREQ][5/6] cpufreq: Changes to get_cpu_idle_time_us(), used by ondemand governor
[CPUFREQ][4/6] cpufreq_ondemand: Parameterize down differential
[CPUFREQ][3/6] cpufreq: get_cpu_idle_time() changes in ondemand for idle-microaccounting
[CPUFREQ][2/6] cpufreq: Change load calculation in ondemand for software coordination
[CPUFREQ][1/6] cpufreq: Add cpu number parameter to __cpufreq_driver_getavg()
[CPUFREQ] use deferrable delayed work init in conservative governor
[CPUFREQ] drivers/cpufreq/cpufreq.c: Adjust error handling code involving cpufreq_cpu_put
[CPUFREQ] add error handling for cpufreq_register_governor() error
[CPUFREQ] acpi-cpufreq: add error handling for cpufreq_register_driver() error
[CPUFREQ] Coding style fixes to arch/x86/kernel/cpu/cpufreq/powernow-k6.c
[CPUFREQ] Coding style fixes to arch/x86/kernel/cpu/cpufreq/elanfreq.c
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governor
export get_cpu_idle_time_us() for it to be used in ondemand governor.
Last update time can be current time when the CPU is currently non-idle,
accounting for the busy time since last idle.
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Dave Jones <davej@redhat.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'rcu-v28-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (21 commits)
rcu: RCU-based detection of stalled CPUs for Classic RCU, fix
rcu: RCU-based detection of stalled CPUs for Classic RCU
rcu: add rcu_read_lock_sched() / rcu_read_unlock_sched()
rcu: fix sparse shadowed variable warning
doc/RCU: fix pseudocode in rcuref.txt
rcuclassic: fix compiler warning
rcu: use irq-safe locks
rcuclassic: fix compilation NG
rcu: fix locking cleanup fallout
rcu: remove redundant ACCESS_ONCE definition from rcupreempt.c
rcu: fix classic RCU locking cleanup lockdep problem
rcu: trace fix possible mem-leak
rcu: just rename call_rcu_bh instead of making it a macro
rcu: remove list_for_each_rcu()
rcu: fixes to include/linux/rcupreempt.h
rcu: classic RCU locking and memory-barrier cleanups
rcu: prevent console flood when one CPU sees another AWOL via RCU
rcu, debug: detect stalled grace periods, cleanups
rcu, debug: detect stalled grace periods
rcu classic: new algorithm for callbacks-processing(v2)
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fix the !CONFIG_RCU_CPU_STALL_DETECTOR path:
kernel/rcuclassic.c: In function '__rcu_pending':
kernel/rcuclassic.c:609: error: too few arguments to function 'check_cpu_stall'
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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This patch adds stalled-CPU detection to Classic RCU. This capability
is enabled by a new config variable CONFIG_RCU_CPU_STALL_DETECTOR, which
defaults disabled.
This is a debugging feature to detect infinite loops in kernel code, not
something that non-kernel-hackers would be expected to care about.
This feature can detect looping CPUs in !PREEMPT builds and looping CPUs
with preemption disabled in PREEMPT builds. This is essentially a port of
this functionality from the treercu patch, replacing the stall debug patch
that is already in tip/core/rcu (commit 67182ae1c4).
The changes from the patch in tip/core/rcu include making the config
variable name match that in treercu, changing from seconds to jiffies to
avoid spurious warnings, and printing a boot message when this feature
is enabled.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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kernel/rcuclassic.c:564:18: warning: symbol 'flags' shadows an earlier one
kernel/rcuclassic.c:527:16: originally declared here
Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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CC kernel/rcuclassic.o
kernel/rcuclassic.c: In function 'rcu_init_percpu_data':
kernel/rcuclassic.c:705: warning: comparison of distinct pointer types lacks a cast
kernel/rcuclassic.c:713: warning: comparison of distinct pointer types lacks a cast
flags should be unsigned long.
Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Some earlier tip/core/rcu patches caused RCU to incorrectly enable irqs
too early in boot. This caused Yinghai's repeated-kexec testing to
hit oopses, presumably due to so that device interrupts left over from
the prior kernel instance (which would oops the newly booting kernel
before it got a chance to reset said devices). This patch therefore
converts all the local_irq_disable()s in rcuclassic.c to local_irq_save().
Besides, I never did like local_irq_disable() anyway. ;-)
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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fix:
CC kernel/rcuclassic.o
kernel/rcuclassic.c: In function '__rcu_process_callbacks':
kernel/rcuclassic.c:561: error: 'flags' undeclared (first use in this function)
kernel/rcuclassic.c:561: error: (Each undeclared identifier is reported only once
kernel/rcuclassic.c:561: error: for each function it appears in.)
Declare missing variable flags.
Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Given that the rcp->lock is now acquired from call_rcu(), which can be
invoked from irq-disable regions, all acquisitions need to disable irqs.
The following patch fixes this.
Although I don't have any reason to believe that this is the cause of
Yinghai's oops, it does need to be fixed.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Remove the redundant definition of ACCESS_ONCE() from rcupreempt.c in
favor of the one in compiler.h. Also merge the comment header from
rcupreempt.c's definition into that in compiler.h.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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On Fri, Aug 15, 2008 at 04:24:30PM +0200, Ingo Molnar wrote:
>
> Paul,
>
> one of your two recent RCU patches caused this lockdep splat in -tip
> testing:
>
> ------------------->
> Brought up 2 CPUs
> Total of 2 processors activated (6850.87 BogoMIPS).
> PM: Adding info for No Bus:platform
> khelper used greatest stack depth: 3124 bytes left
>
> =================================
> [ INFO: inconsistent lock state ]
> 2.6.27-rc3-tip #1
> ---------------------------------
> inconsistent {softirq-on-W} -> {in-softirq-W} usage.
> ksoftirqd/0/4 [HC0[0]:SC1[1]:HE1:SE0] takes:
> (&rcu_ctrlblk.lock){-+..}, at: [<c016d91c>] __rcu_process_callbacks+0x1ac/0x1f0
> {softirq-on-W} state was registered at:
> [<c01528e4>] __lock_acquire+0x3f4/0x5b0
> [<c0152b29>] lock_acquire+0x89/0xc0
> [<c076142b>] _spin_lock+0x3b/0x70
> [<c016d649>] rcu_init_percpu_data+0x29/0x80
> [<c075e43f>] rcu_cpu_notify+0xaf/0xd0
> [<c076458d>] notifier_call_chain+0x2d/0x60
> [<c0145ede>] __raw_notifier_call_chain+0x1e/0x30
> [<c075db29>] _cpu_up+0x79/0x110
> [<c075dc0d>] cpu_up+0x4d/0x70
> [<c0a769e1>] kernel_init+0xb1/0x200
> [<c01048a3>] kernel_thread_helper+0x7/0x10
> [<ffffffff>] 0xffffffff
> irq event stamp: 14
> hardirqs last enabled at (14): [<c01534db>] trace_hardirqs_on+0xb/0x10
> hardirqs last disabled at (13): [<c014dbeb>] trace_hardirqs_off+0xb/0x10
> softirqs last enabled at (0): [<c012b186>] copy_process+0x276/0x1190
> softirqs last disabled at (11): [<c0105c0a>] call_on_stack+0x1a/0x30
>
> other info that might help us debug this:
> no locks held by ksoftirqd/0/4.
>
> stack backtrace:
> Pid: 4, comm: ksoftirqd/0 Not tainted 2.6.27-rc3-tip #1
> [<c01504dc>] print_usage_bug+0x16c/0x1b0
> [<c0152455>] mark_lock+0xa75/0xb10
> [<c0108b75>] ? sched_clock+0x15/0x30
> [<c015289d>] __lock_acquire+0x3ad/0x5b0
> [<c0152b29>] lock_acquire+0x89/0xc0
> [<c016d91c>] ? __rcu_process_callbacks+0x1ac/0x1f0
> [<c076142b>] _spin_lock+0x3b/0x70
> [<c016d91c>] ? __rcu_process_callbacks+0x1ac/0x1f0
> [<c016d91c>] __rcu_process_callbacks+0x1ac/0x1f0
> [<c016d986>] rcu_process_callbacks+0x26/0x50
> [<c0132305>] __do_softirq+0x95/0x120
> [<c0132270>] ? __do_softirq+0x0/0x120
> [<c0105c0a>] call_on_stack+0x1a/0x30
> [<c0132426>] ? ksoftirqd+0x96/0x110
> [<c0132390>] ? ksoftirqd+0x0/0x110
> [<c01411f7>] ? kthread+0x47/0x80
> [<c01411b0>] ? kthread+0x0/0x80
> [<c01048a3>] ? kernel_thread_helper+0x7/0x10
> =======================
> calling init_cpufreq_transition_notifier_list+0x0/0x20
> initcall init_cpufreq_transition_notifier_list+0x0/0x20 returned 0 after 0 msecs
> calling net_ns_init+0x0/0x190
> net_namespace: 676 bytes
> initcall net_ns_init+0x0/0x190 returned 0 after 0 msecs
> calling cpufreq_tsc+0x0/0x20
> initcall cpufreq_tsc+0x0/0x20 returned 0 after 0 msecs
> calling reboot_init+0x0/0x20
> initcall reboot_init+0x0/0x20 returned 0 after 0 msecs
> calling print_banner+0x0/0x10
> Booting paravirtualized kernel on bare hardware
>
> <-----------------------
>
> my guess is on:
>
> commit 1f7b94cd3d564901f9e04a8bc5832ae7bfd690a0
> Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> Date: Tue Aug 5 09:21:44 2008 -0700
>
> rcu: classic RCU locking and memory-barrier cleanups
>
> Ingo
Fixes a problem detected by lockdep in which rcu->lock was acquired
both in irq context and in process context, but without disabling from
process context.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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In the initialization of the RCU trace module, if
rcupreempt_debugfs_init() fails, we never free the the trace buffer.
This patch frees the trace buffer in case the debugfs fails.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Reviewed-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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This patch simplifies the locking and memory-barrier usage in the Classic
RCU grace-period-detection mechanism, incorporating Lai Jiangshan's
feedback from the earlier version (http://lkml.org/lkml/2008/8/1/400
and http://lkml.org/lkml/2008/8/3/43). Passed 10 hours of
rcutorture concurrent with CPUs being put online and taken offline on
a 128-hardware-thread Power machine. My apologies to whoever in the
Eastern Hemisphere was planning to use this machine over the Western
Hemisphere night, but it was sitting idle and...
So this is ready for tip/core/rcu.
This patch is in preparation for moving to a hierarchical
algorithm to allow the very large SMP machines -- requested by some
people at OLS, and there seem to have been a few recent patches in the
4096-CPU direction as well. The general idea is to move to a much more
conservative concurrency design, then apply a hierarchy to reduce
contention on the global lock by a few orders of magnitude (larger
machines would see greater reductions). The reason for taking a
conservative approach is that this code isn't on any fast path.
Prototype in progress.
This patch is against the linux-tip git tree (tip/core/rcu). If you
wish to test this against 2.6.26, use the following set of patches:
http://www.rdrop.com/users/paulmck/patches/2.6.26-ljsimp-1.patch
http://www.rdrop.com/users/paulmck/patches/2.6.26-ljsimpfix-3.patch
The first patch combines commits 5127bed588a2f8f3a1f732de2a8a190b7df5dce3
and 3cac97cbb14aed00d83eb33d4613b0fe3aaea863 from Lai Jiangshan
<laijs@cn.fujitsu.com>, and the second patch contains my changes.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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One small change needed to keep from flooding the console when one
CPU notices that another is AWOL. Unless I am missing something subtle.
Otherwise the cleanups look good!
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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small cleanups.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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this is a diagnostic patch for Classic RCU.
The approach is to record a timestamp at the beginning
of the grace period (in rcu_start_batch()), then have
rcu_check_callbacks() complain if:
1. it is running on a CPU that has holding up grace periods for
a long time (say one second). This will identify the culprit
assuming that the culprit has not disabled hardware irqs,
instruction execution, or some such.
2. it is running on a CPU that is not holding up grace periods,
but grace periods have been held up for an even longer time
(say two seconds).
It is enabled via the default-off CONFIG_DEBUG_RCU_STALL kernel parameter.
Rather than exponential backoff, it backs off to once per 30 seconds.
My feeling upon thinking on it was that if you have stalled RCU grace
periods for that long, a few extra printk() messages are probably the
least of your worries...
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Yinghai Lu <yhlu.kernel@gmail.com>
Cc: David Witbrodt <dawitbro@sbcglobal.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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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>
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