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  1. 16 1月, 2015 5 次提交
    • P
      rcu: Initialize tiny RCU stall-warning timeouts at boot · 630181c4
      由 Paul E. McKenney 提交于 
      The current tiny RCU stall-warning code assumes that the jiffies counter
starts at zero, however, it is sometimes initialized to other values,
for example, -30,000.  This commit therefore changes rcu_init() to
invoke reset_cpu_stall_ticks() for both flavors of RCU to initialize
the stall-warning times properly at boot.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      630181c4
    • M
      rcu: Fix RCU CPU stall detection in tiny implementation · ec1fe396
      由 Miroslav Benes 提交于 
      The tiny RCU CPU stall detection depends on *rcp->curtail not being
NULL. It is however a tail pointer and thus NULL by definition. Instead we
should check rcp->rcucblist for the presence of pending callbacks which
need to be processed. With this fix INFO about the stall is printed and
jiffies_stall (jiffies at next stall) correctly updated.

Note that the check for pending callback is necessary to avoid spurious
warnings if there are no pendings callbacks.
Signed-off-by: NMiroslav Benes <mbenes@suse.cz>
[ paulmck: Fused identical "if" statements, ported to -rcu. ]
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      ec1fe396
    • P
      rcu: Add GP-kthread-starvation checks to CPU stall warnings · fb81a44b
      由 Paul E. McKenney 提交于 
      This commit adds a message that is printed if the relevant grace-period
kthread has not been able to run for the two seconds preceding the
stall warning.  (The two seconds is double the maximum interval between
successive bouts of quiescent-state forcing.)
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      fb81a44b
    • P
      rcu: Make cond_resched_rcu_qs() apply to normal RCU flavors · 5cd37193
      由 Paul E. McKenney 提交于 
      Although cond_resched_rcu_qs() only applies to TASKS_RCU, it is used
in places where it would be useful for it to apply to the normal RCU
flavors, rcu_preempt, rcu_sched, and rcu_bh.  This is especially the
case for workloads that aggressively overload the system, particularly
those that generate large numbers of RCU updates on systems running
NO_HZ_FULL CPUs.  This commit therefore communicates quiescent states
from cond_resched_rcu_qs() to the normal RCU flavors.

Note that it is unfortunately necessary to leave the old ->passed_quiesce
mechanism in place to allow quiescent states that apply to only one
flavor to be recorded.  (Yes, we could decrement ->rcu_qs_ctr_snap in
that case, but that is not so good for debugging of RCU internals.)
In addition, if one of the RCU flavor's grace period has stalled, this
will invoke rcu_momentary_dyntick_idle(), resulting in a heavy-weight
quiescent state visible from other CPUs.
Reported-by: NSasha Levin <sasha.levin@oracle.com>
Reported-by: NDave Jones <davej@redhat.com>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: Merge commit from Sasha Levin fixing a bug where __this_cpu()
  was used in preemptible code. ]
      5cd37193
    • P
      rcu: Optionally run grace-period kthreads at real-time priority · a94844b2
      由 Paul E. McKenney 提交于 
      Recent testing has shown that under heavy load, running RCU's grace-period
kthreads at real-time priority can improve performance (according to 0day
test robot) and reduce the incidence of RCU CPU stall warnings.  However,
most systems do just fine with the default non-realtime priorities for
these kthreads, and it does not make sense to expose the entire user
base to any risk stemming from this change, given that this change is
of use only to a few users running extremely heavy workloads.

Therefore, this commit allows users to specify realtime priorities
for the grace-period kthreads, but leaves them running SCHED_OTHER
by default.  The realtime priority may be specified at build time
via the RCU_KTHREAD_PRIO Kconfig parameter, or at boot time via the
rcutree.kthread_prio parameter.  Either way, 0 says to continue the
default SCHED_OTHER behavior and values from 1-99 specify that priority
of SCHED_FIFO behavior.  Note that a value of 0 is not permitted when
the RCU_BOOST Kconfig parameter is specified.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      a94844b2
  3. 07 1月, 2015 5 次提交
    • P
      rcu: Handle gpnum/completed wrap while dyntick idle · e3663b10
      由 Paul E. McKenney 提交于 
      Subtle race conditions can result if a CPU stays in dyntick-idle mode
long enough for the ->gpnum and ->completed fields to wrap.  For
example, consider the following sequence of events:

o	CPU 1 encounters a quiescent state while waiting for grace period
	5 to complete, but then enters dyntick-idle mode.

o	While CPU 1 is in dyntick-idle mode, the grace-period counters
	wrap around so that the grace period number is now 4.

o	Just as CPU 1 exits dyntick-idle mode, grace period 4 completes
	and grace period 5 begins.

o	The quiescent state that CPU 1 passed through during the old
	grace period 5 looks like it applies to the new grace period
	5.  Therefore, the new grace period 5 completes without CPU 1
	having passed through a quiescent state.

This could clearly be a fatal surprise to any long-running RCU read-side
critical section that happened to be running on CPU 1 at the time.  At one
time, this was not a problem, given that it takes significant time for
the grace-period counters to overflow even on 32-bit systems.  However,
with the advent of NO_HZ_FULL and SMP embedded systems, arbitrarily long
idle periods are now becoming quite feasible.  It is therefore time to
close this race.

This commit therefore avoids this race condition by having the
quiescent-state forcing code detect when a CPU is falling too far
behind, and setting a new rcu_data field ->gpwrap when this happens.
Whenever this new ->gpwrap field is set, the CPU's ->gpnum and ->completed
fields are known to be untrustworthy, and can be ignored, along with
any associated quiescent states.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      e3663b10
    • P
      rcu: Improve diagnostics for spurious RCU CPU stall warnings · 6ccd2ecd
      由 Paul E. McKenney 提交于 
      The current RCU CPU stall warning code will print "Stall ended before
state dump start" any time that the stall-warning code is triggered on
a CPU that has already reported a quiescent state for the current grace
period and if all quiescent states have been reported for the current
grace period.  However, a true stall can result in these symptoms, for
example, by preventing RCU's grace-period kthreads from ever running

This commit therefore checks for this condition, reporting the end of
the stall only if one of the grace-period counters has actually advanced.
Otherwise, it reports the last time that the grace-period kthread made
meaningful progress.  (In normal situations, the grace-period kthread
should make meaningful progress at least every jiffies_till_next_fqs
jiffies.)
Reported-by: NMiroslav Benes <mbenes@suse.cz>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: NMiroslav Benes <mbenes@suse.cz>
      6ccd2ecd
    • P
      rcu: Make RCU_CPU_STALL_INFO include number of fqs attempts · fc908ed3
      由 Paul E. McKenney 提交于 
      One way that an RCU CPU stall warning can happen is if the grace-period
kthread is not allowed to execute.  One proxy for this kthread's
forward progress is the number of force-quiescent-state (fqs) scans.
This commit therefore adds the number of fqs scans to the RCU CPU stall
warning printouts when CONFIG_RCU_CPU_STALL_INFO=y.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      fc908ed3
    • P
      rcutorture: Add checks for stall ending before dump start · e9408e4f
      由 Paul E. McKenney 提交于 
      The current rcutorture scripting checks for actual stalls (via the "Call
Trace:" check), but fails to spot the case where a stall ends just as it
is being detected.  This commit therefore adds a check for this case.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      e9408e4f
    • P
      rcu: Set default to RCU_CPU_STALL_INFO=y · 68158fe2
      由 Paul E. McKenney 提交于 
      The RCU_CPU_STALL_INFO code has been in for quite some time, and has
proven reliable.  This commit therefore enables it by default.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      68158fe2
  5. 31 12月, 2014 1 次提交
    • P
      rcu: Make rcu_nmi_enter() handle nesting · 734d1680
      由 Paul E. McKenney 提交于 
      The x86 architecture has multiple types of NMI-like interrupts: real
NMIs, machine checks, and, for some values of NMI-like, debugging
and breakpoint interrupts.  These interrupts can nest inside each
other.  Andy Lutomirski is adding RCU support to these interrupts,
so rcu_nmi_enter() and rcu_nmi_exit() must now correctly handle nesting.

This commit therefore introduces nesting, using a clever NMI-coordination
algorithm suggested by Andy.  The trick is to atomically increment
->dynticks (if needed) before manipulating ->dynticks_nmi_nesting on entry
(and, accordingly, after on exit).  In addition, ->dynticks_nmi_nesting
is incremented by one if ->dynticks was incremented and by two otherwise.
This means that when rcu_nmi_exit() sees ->dynticks_nmi_nesting equal
to one, it knows that ->dynticks must be atomically incremented.

This NMI-coordination algorithms has been validated by the following
Promela model:

------------------------------------------------------------------------

/*
 * Promela model for Andy Lutomirski's suggested change to rcu_nmi_enter()
 * that allows nesting.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, you can access it online at
 * http://www.gnu.org/licenses/gpl-2.0.html.
 *
 * Copyright IBM Corporation, 2014
 *
 * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
 */

byte dynticks_nmi_nesting = 0;
byte dynticks = 0;

/*
 * Promela verision of rcu_nmi_enter().
 */
inline rcu_nmi_enter()
{
	byte incby;
	byte tmp;

	incby = BUSY_INCBY;
	assert(dynticks_nmi_nesting >= 0);
	if
	:: (dynticks & 1) == 0 ->
		atomic {
			dynticks = dynticks + 1;
		}
		assert((dynticks & 1) == 1);
		incby = 1;
	:: else ->
		skip;
	fi;
	tmp = dynticks_nmi_nesting;
	tmp = tmp + incby;
	dynticks_nmi_nesting = tmp;
	assert(dynticks_nmi_nesting >= 1);
}

/*
 * Promela verision of rcu_nmi_exit().
 */
inline rcu_nmi_exit()
{
	byte tmp;

	assert(dynticks_nmi_nesting > 0);
	assert((dynticks & 1) != 0);
	if
	:: dynticks_nmi_nesting != 1 ->
		tmp = dynticks_nmi_nesting;
		tmp = tmp - BUSY_INCBY;
		dynticks_nmi_nesting = tmp;
	:: else ->
		dynticks_nmi_nesting = 0;
		atomic {
			dynticks = dynticks + 1;
		}
		assert((dynticks & 1) == 0);
	fi;
}

/*
 * Base-level NMI runs non-atomically.  Crudely emulates process-level
 * dynticks-idle entry/exit.
 */
proctype base_NMI()
{
	byte busy;

	busy = 0;
	do
	::	/* Emulate base-level dynticks and not. */
		if
		:: 1 ->	atomic {
				dynticks = dynticks + 1;
			}
			busy = 1;
		:: 1 ->	skip;
		fi;

		/* Verify that we only sometimes have base-level dynticks. */
		if
		:: busy == 0 -> skip;
		:: busy == 1 -> skip;
		fi;

		/* Model RCU's NMI entry and exit actions. */
		rcu_nmi_enter();
		assert((dynticks & 1) == 1);
		rcu_nmi_exit();

		/* Emulated re-entering base-level dynticks and not. */
		if
		:: !busy -> skip;
		:: busy ->
			atomic {
				dynticks = dynticks + 1;
			}
			busy = 0;
		fi;

		/* We had better now be in dyntick-idle mode. */
		assert((dynticks & 1) == 0);
	od;
}

/*
 * Nested NMI runs atomically to emulate interrupting base_level().
 */
proctype nested_NMI()
{
	do
	::	/*
		 * Use an atomic section to model a nested NMI.  This is
		 * guaranteed to interleave into base_NMI() between a pair
		 * of base_NMI() statements, just as a nested NMI would.
		 */
		atomic {
			/* Verify that we only sometimes are in dynticks. */
			if
			:: (dynticks & 1) == 0 -> skip;
			:: (dynticks & 1) == 1 -> skip;
			fi;

			/* Model RCU's NMI entry and exit actions. */
			rcu_nmi_enter();
			assert((dynticks & 1) == 1);
			rcu_nmi_exit();
		}
	od;
}

init {
	run base_NMI();
	run nested_NMI();
}

------------------------------------------------------------------------

The following script can be used to run this model if placed in
rcu_nmi.spin:

------------------------------------------------------------------------

if ! spin -a rcu_nmi.spin
then
	echo Spin errors!!!
	exit 1
fi
if ! cc -DSAFETY -o pan pan.c
then
	echo Compilation errors!!!
	exit 1
fi
./pan -m100000
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: NLai Jiangshan <laijs@cn.fujitsu.com>
      734d1680
  7. 21 12月, 2014 8 次提交
    • L
      Linux 3.19-rc1 · 97bf6af1
      由 Linus Torvalds 提交于
      97bf6af1
    • L
      Merge tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/borntraeger/linux · 60815cf2
      由 Linus Torvalds 提交于 
      Pull ACCESS_ONCE cleanup preparation from Christian Borntraeger:
 "kernel: Provide READ_ONCE and ASSIGN_ONCE

  As discussed on LKML http://marc.info/?i=54611D86.4040306%40de.ibm.com
  ACCESS_ONCE might fail with specific compilers for non-scalar
  accesses.

  Here is a set of patches to tackle that problem.

  The first patch introduce READ_ONCE and ASSIGN_ONCE.  If the data
  structure is larger than the machine word size memcpy is used and a
  warning is emitted.  The next patches fix up several in-tree users of
  ACCESS_ONCE on non-scalar types.

  This does not yet contain a patch that forces ACCESS_ONCE to work only
  on scalar types.  This is targetted for the next merge window as Linux
  next already contains new offenders regarding ACCESS_ONCE vs.
  non-scalar types"

* tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/borntraeger/linux:
  s390/kvm: REPLACE barrier fixup with READ_ONCE
  arm/spinlock: Replace ACCESS_ONCE with READ_ONCE
  arm64/spinlock: Replace ACCESS_ONCE READ_ONCE
  mips/gup: Replace ACCESS_ONCE with READ_ONCE
  x86/gup: Replace ACCESS_ONCE with READ_ONCE
  x86/spinlock: Replace ACCESS_ONCE with READ_ONCE
  mm: replace ACCESS_ONCE with READ_ONCE or barriers
  kernel: Provide READ_ONCE and ASSIGN_ONCE
      60815cf2
    • L
      Merge tag 'clk-for-linus-3.19' of git://git.linaro.org/people/mike.turquette/linux · bfc7249c
      由 Linus Torvalds 提交于 
      Pull clk framework updates from Mike Turquette:
 "This is much later than usual due to several last minute bugs that had
  to be addressed.  As usual the majority of changes are new drivers and
  modifications to existing drivers.  The core recieved many fixes along
  with the groundwork for several large changes coming in the future
  which will better parition clock providers from clock consumers"

* tag 'clk-for-linus-3.19' of git://git.linaro.org/people/mike.turquette/linux: (86 commits)
  clk: samsung: Fix Exynos 5420 pinctrl setup and clock disable failure due to domain being gated
  ARM: OMAP3: clock: fix boot breakage in legacy mode
  ARM: OMAP2+: clock: fix DPLL code to use new determine rate APIs
  clk: Really fix deadlock with mmap_sem
  clk: mmp: fix sparse non static symbol warning
  clk: Change clk_ops->determine_rate to return a clk_hw as the best parent
  clk: change clk_debugfs_add_file to take a struct clk_hw
  clk: Don't expose __clk_get_accuracy
  clk: Don't try to use a struct clk* after it could have been freed
  clk: Remove unused function __clk_get_prepare_count
  clk: samsung: Fix double add of syscore ops after driver rebind
  clk: samsung: exynos4: set parent of sclk_hdmiphy to hdmi
  clk: samsung: exynos4415: Fix build with PM_SLEEP disabled
  clk: samsung: remove unnecessary inclusion of header files from clk.h
  clk: samsung: remove unnecessary CONFIG_OF from clk.c
  clk: samsung: Spelling s/bwtween/between/
  clk: rockchip: Add support for the mmc clock phases using the framework
  clk: rockchip: add bindings for the mmc clocks
  clk: rockchip: rk3288 export i2s0_clkout for use in DT
  clk: rockchip: use clock ID for DMC (memory controller) on rk3288
  ...
      bfc7249c
    • L
      Merge branch 'i2c/for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux · a4e1328a
      由 Linus Torvalds 提交于 
      Pull more i2c updates from Wolfram Sang:
 "Included are two bugfixes needing some bigger refactoring (sh_mobile:
  deferred probe with DMA, mv64xxx: fix offload support) and one
  deprecated driver removal I thought would go in via ppc but I
  misunderstood.  It has a proper ack from BenH"

* 'i2c/for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux:
  i2c: sh_mobile: fix uninitialized var when debug is enabled
  macintosh: therm_pm72: delete deprecated driver
  i2c: sh_mobile: I2C_SH_MOBILE should depend on HAS_DMA
  i2c: sh_mobile: rework deferred probing
  i2c: sh_mobile: refactor DMA setup
  i2c: mv64xxx: rework offload support to fix several problems
  i2c: mv64xxx: use BIT() macro for register value definitions
      a4e1328a
    • L
      Merge tag 'scsi-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi · cdce6ac2
      由 Linus Torvalds 提交于 
      Pull SCSI update from James Bottomley:
 "This is a much shorter set of patches that were on the go but didn't
  make it in to the early pull request for the merge window.  It's
  really a set of bug fixes plus some final cleanup work on the new tag
  queue API"

* tag 'scsi-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
  storvsc: ring buffer failures may result in I/O freeze
  ipr: set scsi_level correctly for disk arrays
  ipr: add support for async scanning to speed up boot
  scsi_debug: fix missing "break;" in SDEBUG_UA_CAPACITY_CHANGED case
  scsi_debug: take sdebug_host_list_lock when changing capacity
  scsi_debug: improve driver description in Kconfig
  scsi_debug: fix compare and write errors
  qla2xxx: fix race in handling rport deletion during recovery causes panic
  scsi: blacklist RSOC for Microsoft iSCSI target devices
  scsi: fix random memory corruption with scsi-mq + T10 PI
  Revert "[SCSI] mpt3sas: Remove phys on topology change"
  Revert "[SCSI] mpt2sas: Remove phys on topology change."
  esas2r: Correct typos of "validate" in a comment
  fc: FCP_PTA_SIMPLE is 0
  ibmvfc: remove unused tag variable
  scsi: remove MSG_*_TAG defines
  scsi: remove scsi_set_tag_type
  scsi: remove scsi_get_tag_type
  scsi: never drop to untagged mode during queue ramp down
  scsi: remove ->change_queue_type method
      cdce6ac2
    • L
      Merge tag 'pm-config-3.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm · 5d6a5468
      由 Linus Torvalds 提交于 
      Pull CONFIG_PM_RUNTIME elimination from Rafael Wysocki:
 "This removes the last few uses of CONFIG_PM_RUNTIME introduced
  recently and makes that config option finally go away.

  CONFIG_PM will be available directly from the menu now and also it
  will be selected automatically if CONFIG_SUSPEND or CONFIG_HIBERNATION
  is set"

* tag 'pm-config-3.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  PM: Eliminate CONFIG_PM_RUNTIME
  tty: 8250_omap: Replace CONFIG_PM_RUNTIME with CONFIG_PM
  sound: sst-haswell-pcm: Replace CONFIG_PM_RUNTIME with CONFIG_PM
  spi: Replace CONFIG_PM_RUNTIME with CONFIG_PM
      5d6a5468
    • L
      Merge branch 'misc' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild · 787140ad
      由 Linus Torvalds 提交于 
      Pull misc kbuild changes from Michal Marek:
 "There are only a few things in the misc branch:

   - Fix for bugon.cocci semantic patch
   - Kdevelop4 files are .gitignored
   - Put make binrpm-pkg on diet"

* 'misc' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild:
  scripts/package: binrpm-pkg do not create source and devel package
  .gitignore: Add Kdevelop4 project files
  bugon.cocci: fix Options at the macro
      787140ad
    • L
      Merge branch 'kbuild' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild · d08372ca
      由 Linus Torvalds 提交于 
      Pull kbuild updates from Michal Marek:
 "Here are the kbuild changes for v3.19-rc1:

   - Cleanups and deduplication in the main Makefile and
     scripts/Makefile.*
   - Sort the output of *config targets in make help
   - Old <linux/version.h> is always removed to avoid a surprise during
     bisecting
   - Warning fix in kconfig"

* 'kbuild' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild:
  kbuild: remove redundant -rR flag of hdr-inst
  kbuild: Fix make help-<board series> on powerpc
  kbuild: Automatically remove stale <linux/version.h> file
  kconfig: Fix warning "‘jump’ may be used uninitialized"
  Makefile: sort list of defconfig targets in make help output
  kbuild: Remove duplicate $(cmd) definition in Makefile.clean
  kbuild: collect shorthands into scripts/Kbuild.include
      d08372ca
  9. 20 12月, 2014 21 次提交