11 May, 2010
17 commits
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Lai Jiangshan noted that up to 10% of the RCU_SOFTIRQ are spurious, and
traced this down to the fact that the current grace-period machinery
will uselessly raise RCU_SOFTIRQ when a given CPU needs to go through
a quiescent state, but has not yet done so. In this situation, there
might well be nothing that RCU_SOFTIRQ can do, and the overhead can be
worth worrying about in the ksoftirqd case. This patch therefore avoids
raising RCU_SOFTIRQ in this situation.Changes since v1 (http://lkml.org/lkml/2010/3/30/122 from Lai Jiangshan):
o Omit the rcu_qs_pending() prechecks, as they aren't that
much less expensive than the quiescent-state checks.o Merge with the set_need_resched() patch that reduces IPIs.
o Add the new n_rp_report_qs field to the rcu_pending tracing output.
o Update the tracing documentation accordingly.
Signed-off-by: Lai Jiangshan
Signed-off-by: Paul E. McKenney -
TREE_RCU assumes that CPU numbering is contiguous, but some users need
large holes in the numbering to better map to hardware layout. This patch
makes TREE_RCU (and TREE_PREEMPT_RCU) tolerate large holes in the CPU
numbering. However, NR_CPUS must still be greater than the largest
CPU number.Signed-off-by: Paul E. McKenney
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The existing RCU CPU stall-warning messages can be confusing, especially
in the case where one CPU detects a single other stalled CPU. In addition,
the console messages did not say which flavor of RCU detected the stall,
which can make it difficult to work out exactly what is causing the stall.
This commit improves these messages.Requested-by: Dhaval Giani
Signed-off-by: Paul E. McKenney -
Print boot-time messages if tracing is enabled, if fanout is set
to non-default values, if exact fanout is specified, if accelerated
dyntick-idle grace periods have been enabled, if RCU-lockdep is enabled,
if rcutorture has been boot-time enabled, if the CPU stall detector has
been disabled, or if four-level hierarchy has been enabled.This is all for TREE_RCU and TREE_PREEMPT_RCU. TINY_RCU will be handled
separately, if at all.Suggested-by: Josh Triplett
Signed-off-by: Paul E. McKenney -
The current RCU CPU stall warnings remain enabled even after a panic
occurs, which some people have found to be a bit counterproductive.
This patch therefore uses a notifier to disable stall warnings once a
panic occurs.Signed-off-by: Paul E. McKenney
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The CPU_STALL_VERBOSE kernel configuration parameter was added to
2.6.34 to identify any preempted/blocked tasks that were preventing
the current grace period from completing when running preemptible
RCU. As is conventional for new configurations parameters, this
defaulted disabled. It is now time to enable it by default.Signed-off-by: Paul E. McKenney
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TINY_RCU does not need rcu_scheduler_active unless CONFIG_DEBUG_LOCK_ALLOC.
So conditionally compile rcu_scheduler_active in order to slim down
rcutiny a bit more. Also gets rid of an EXPORT_SYMBOL_GPL, which is
responsible for most of the slimming.Signed-off-by: Paul E. McKenney
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The addition of preemptible RCU to treercu resulted in a bit of
confusion and inefficiency surrounding the handling of context switches
for RCU-sched and for RCU-preempt. For RCU-sched, a context switch
is a quiescent state, pure and simple, just like it always has been.
For RCU-preempt, a context switch is in no way a quiescent state, but
special handling is required when a task blocks in an RCU read-side
critical section.However, the callout from the scheduler and the outer loop in ksoftirqd
still calls something named rcu_sched_qs(), whose name is no longer
accurate. Furthermore, when rcu_check_callbacks() notes an RCU-sched
quiescent state, it ends up unnecessarily (though harmlessly, aside
from the performance hit) enqueuing the current task if it happens to
be running in an RCU-preempt read-side critical section. This not only
increases the maximum latency of scheduler_tick(), it also needlessly
increases the overhead of the next outermost rcu_read_unlock() invocation.This patch addresses this situation by separating the notion of RCU's
context-switch handling from that of RCU-sched's quiescent states.
The context-switch handling is covered by rcu_note_context_switch() in
general and by rcu_preempt_note_context_switch() for preemptible RCU.
This permits rcu_sched_qs() to handle quiescent states and only quiescent
states. It also reduces the maximum latency of scheduler_tick(), though
probably by much less than a microsecond. Finally, it means that tasks
within preemptible-RCU read-side critical sections avoid incurring the
overhead of queuing unless there really is a context switch.Suggested-by: Lai Jiangshan
Acked-by: Lai Jiangshan
Signed-off-by: Paul E. McKenney
Cc: Ingo Molnar
Cc: Peter Zijlstra -
Make naming line up in preparation for CONFIG_TINY_PREEMPT_RCU.
Signed-off-by: Paul E. McKenney
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Because synchronize_rcu_bh() is identical to synchronize_sched(),
make the former a static inline invoking the latter, saving the
overhead of an EXPORT_SYMBOL_GPL() and the duplicate code.Signed-off-by: Paul E. McKenney
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The rcu_scheduler_active check has been wrapped into the new
debug_lockdep_rcu_enabled() function, so update the comments to
reflect this new reality.Signed-off-by: Paul E. McKenney
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It is CONFIG_DEBUG_LOCK_ALLOC rather than CONFIG_PROVE_LOCKING, so fix it.
Signed-off-by: Paul E. McKenney
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Offline CPUs are not in nohz_cpu_mask, but can be ignored when checking
for the last non-dyntick-idle CPU. This patch therefore only checks
online CPUs for not being dyntick idle, allowing fast entry into
full-system dyntick-idle state even when there are some offline CPUs.Signed-off-by: Lai Jiangshan
Signed-off-by: Paul E. McKenney -
Shrink the RCU_INIT_FLAVOR() macro by moving all but the initialization
of the ->rda[] array to rcu_init_one(). The call to rcu_init_one()
can then be moved to the end of the RCU_INIT_FLAVOR() macro, which is
required because rcu_boot_init_percpu_data(), which is now called from
rcu_init_one(), depends on the initialization of the ->rda[] array.Signed-off-by: Lai Jiangshan
Signed-off-by: Paul E. McKenney -
cleanup: make dead code really dead
Signed-off-by: Lai Jiangshan
Signed-off-by: Paul E. McKenney -
This patch adds a check to __rcu_pending() that does a local
set_need_resched() if the current CPU is holding up the current grace
period and if force_quiescent_state() will be called soon. The goal is
to reduce the probability that force_quiescent_state() will need to do
smp_send_reschedule(), which sends an IPI and is therefore more expensive
on most architectures.Signed-off-by: "Paul E. McKenney"
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There is no need to disable lockdep after an RCU lockdep splat,
so remove the debug_lockdeps_off() from lockdep_rcu_dereference().
To avoid repeated lockdep splats, use a static variable in the inlined
rcu_dereference_check() and rcu_dereference_protected() macros so that
a given instance splats only once, but so that multiple instances can
be detected per boot.This is controlled by a new config variable CONFIG_PROVE_RCU_REPEATEDLY,
which is disabled by default. This provides the normal lockdep behavior
by default, but permits people who want to find multiple RCU-lockdep
splats per boot to easily do so.Requested-by: Eric Paris
Signed-off-by: Lai Jiangshan
Tested-by: Eric Paris
Signed-off-by: Paul E. McKenney
10 May, 2010
3 commits
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* git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi-rc-fixes-2.6:
[SCSI] Retry commands with UNIT_ATTENTION sense codes to fix ext3/ext4 I/O error
[SCSI] Enable retries for SYNCRONIZE_CACHE commands to fix I/O error
[SCSI] scsi_debug: virtual_gb ignores sector_size
[SCSI] libiscsi: regression: fix header digest errors
[SCSI] fix locking around blk_abort_request()
[SCSI] advansys: fix narrow board error path -
commit 672917dcc78 ("cpuidle: menu governor: reduce latency on exit")
added an optimization, where the analysis on the past idle period moved
from the end of idle, to the beginning of the new idle.Unfortunately, this optimization had a bug where it zeroed one key
variable for new use, that is needed for the analysis. The fix is
simple, zero the variable after doing the work from the previous idle.During the audit of the code that found this issue, another issue was
also found; the ->measured_us data structure member is never set, a
local variable is always used instead.Signed-off-by: Arjan van de Ven
Cc: Corrado Zoccolo
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds
08 May, 2010
9 commits
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* 'for-linus' of git://neil.brown.name/md:
md: restore ability of spare drives to spin down.
md/raid6: Fix raid-6 read-error correction in degraded state -
* 'urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/brodo/pcmcia-2.6:
pcmcia: fix compilation after 16bit state locking changes
pcmcia: order userspace suspend and resume requests
pcmcia: avoid pccard_validate_cis failure in resume callpath -
* 'for-linus' of git://git.kernel.dk/linux-2.6-block:
blk-cgroup: Fix an RCU warning in blkiocg_create()
blk-cgroup: Fix RCU correctness warning in cfq_init_queue()
drbd: don't expose failed local READ to upper layers -
* 'drm-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/airlied/drm-2.6:
drm/ttm: Remove the ttm_bo_block_reservation() function.
drm/ttm: Remove some leftover debug messages.
drm/radeon: async event synchronization for drmWaitVblank -
Move initialization of the virtio framework before the initialization of
mtd, so that block2mtd can be used on virtio-based block devices.Addresses https://bugzilla.kernel.org/show_bug.cgi?id=15644
Signed-off-by: Stijn Tintel
Signed-off-by: Rusty Russell
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds -
* 'bugfixes' of git://git.linux-nfs.org/projects/trondmy/nfs-2.6:
NFS: Fix RCU issues in the NFSv4 delegation code
NFSv4: Fix the locking in nfs_inode_reclaim_delegation() -
* 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-acpi-2.6:
ACPI: sleep: init_set_sci_en_on_resume for Dell Studio 155x
ACPI: fix acpi_hest_firmware_first_pci() caused oops
sbshc: acpi_device_class "smbus_host_controller" too long
power_meter: acpi_device_class "power_meter_resource" too long
acpi_pad: "processor_aggregator" name too long
PNP: don't check for conflicts with bridge windows
ACPI: DMI init_set_sci_en_on_resume for multiple Lenovo ThinkPads
PNPACPI: compute Address Space length rather than using _LEN
ACPI: silence kmemcheck false positive -
* 'v4l_for_2.6.34' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-2.6:
V4L/DVB: pxa_camera: move fifo reset direct before dma start
V4L/DVB: video: testing unsigned for less than 0
V4L/DVB: mx1-camera: compile fix
V4L/DVB: budget: Oops: "BUG: unable to handle kernel NULL pointer dereference"
V4L/DVB: ngene: Workaround for stuck DiSEqC pin
V4L/DVB: saa7146: fix regression of the av7110/budget-av driver
V4L/DVB: v4l: fix config dependencies: mxb and saa7191 are V4L2 drivers, not V4L1
V4L/DVB: feature-removal: announce videotext.h removal
V4L/DVB: V4L - vpfe capture - fix for kernel crash
V4L/DVB: gspca: make usb id 0461:0815 get handled by the right driver
V4L/DVB: gspca - stv06xx: Remove the 046d:08da from the stv06xx driver
V4L/DVB: gspca - sn9c20x: Correct onstack wait_queue_head declaration
V4L/DVB: saa7146: fix up bytesperline if it is an impossible value
V4L/DVB: V4L: vpfe_capture - free ccdc_lock when memory allocation fails
V4L/DVB: V4L - Makfile:Removed duplicate entry of davinci
V4L/DVB: omap24xxcam: potential buffer overflow -
…/git/tip/linux-2.6-tip
* 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
rcu: create rcu_my_thread_group_empty() wrapper
memcg: css_id() must be called under rcu_read_lock()
cgroup: Check task_lock in task_subsys_state()
sched: Fix an RCU warning in print_task()
cgroup: Fix an RCU warning in alloc_css_id()
cgroup: Fix an RCU warning in cgroup_path()
KEYS: Fix an RCU warning in the reading of user keys
KEYS: Fix an RCU warning
07 May, 2010
11 commits
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Some time ago we stopped the clean/active metadata updates
from being written to a 'spare' device in most cases so that
it could spin down and say spun down. Device failure/removal
etc are still recorded on spares.However commit 51d5668cb2e3fd1827a55 broke this 50% of the time,
depending on whether the event count is even or odd.
The change log entry said:This means that the alignment between 'odd/even' and
'clean/dirty' might take a little longer to attain,how ever the code makes no attempt to create that alignment, so it
could take arbitrarily long.So when we find that clean/dirty is not aligned with odd/even,
force a second metadata-update immediately. There are already cases
where a second metadata-update is needed immediately (e.g. when a
device fails during the metadata update). We just piggy-back on that.Reported-by: Joe Bryant
Signed-off-by: NeilBrown
Cc: stable@kernel.org -
Fix: Raid-6 was not trying to correct a read-error when in
singly-degraded state and was instead dropping one more device, going to
doubly-degraded state. This patch fixes this behaviour.Tested-by: Janos Haar
Signed-off-by: Gabriele A. Trombetti
Reported-by: Janos Haar
Signed-off-by: NeilBrown
Cc: stable@kernel.org -
with CONFIG_PROVE_RCU=y, a warning can be triggered:
# mount -t cgroup -o blkio xxx /mnt
# mkdir /mnt/subgroup...
kernel/cgroup.c:4442 invoked rcu_dereference_check() without protection!
...To fix this, we avoid caling css_depth() here, which is a bit simpler
than the original code.Signed-off-by: Li Zefan
Acked-by: Vivek Goyal
Signed-off-by: Jens Axboe -
…5903' and 'misc-2.6.34' into release
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It's unused and buggy in its current form, since it can place a bo
in the reserved state without removing it from lru lists.Signed-off-by: Thomas Hellstrom
Signed-off-by: Dave Airlie -
Signed-off-by: Thomas Hellstrom
Signed-off-by: Dave Airlie -
Bring radeon up to speed with the async event synchronization for
drmWaitVblank. See c9a9c5e02aedc1a2815877b0268f886d2640b771 for
more information. Without this patch event never get delivered
to userspace client.Signed-off-by: Jerome Glisse
Signed-off-by: Dave Airlie -
Move the fifo reset from pxa_camera_start_capture to pxa_camera_irq direct
before the dma start after an end of frame interrupt to prevent images from
shifting because of old data at the begin of the frame.Signed-off-by: Stefan Herbrechtsmeier
Acked-by: Robert Jarzmik
Tested-by: Antonio Ospite
Signed-off-by: Guennadi Liakhovetski
Signed-off-by: Mauro Carvalho Chehab -
soc_mbus_bytes_per_line() returns -EINVAL on error but we store it in an
unsigned int so the test for less than zero doesn't work. I think it
always returns "small" positive values so we can just cast it to int
here.Signed-off-by: Dan Carpenter
Signed-off-by: Guennadi Liakhovetski
Signed-off-by: Mauro Carvalho Chehab -
This fixes a regression of
7d58289 (mx1: prefix SOC specific defines with MX1_ and deprecate old names)
Signed-off-by: Uwe Kleine-König
Acked-by: Sascha Hauer
Signed-off-by: Guennadi Liakhovetski
Signed-off-by: Mauro Carvalho Chehab -
Never call dvb_frontend_detach if we failed to attach a frontend. This fixes
the following oops, which will be triggered by a missing stv090x module:[ 8.172997] DVB: registering new adapter (TT-Budget S2-1600 PCI)
[ 8.209018] adapter has MAC addr = 00:d0:5c:cc:a7:29
[ 8.328665] Intel ICH 0000:00:1f.5: PCI INT B -> GSI 17 (level, low) -> IRQ 17
[ 8.328753] Intel ICH 0000:00:1f.5: setting latency timer to 64
[ 8.562047] DVB: Unable to find symbol stv090x_attach()
[ 8.562117] BUG: unable to handle kernel NULL pointer dereference at 000000ac
[ 8.562239] IP: [] dvb_frontend_detach+0x4/0x67 [dvb_core]Ref http://bugs.debian.org/575207
Signed-off-by: Bjørn Mork
Cc: stable@kernel.org
Signed-off-by: Mauro Carvalho Chehab
