Merge branch 'core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip (5f34fe1c) · Commits · 戴 / test

Documentation/RCU/00-INDEX

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Original line number	Diff line number	Diff line
		@@ -16,6 +16,8 @@ RTFP.txt
		- List of RCU papers (bibliography) going back to 1980.
		torture.txt
		- RCU Torture Test Operation (CONFIG_RCU_TORTURE_TEST)
		trace.txt
		- CONFIG_RCU_TRACE debugfs files and formats
		UP.txt
		- RCU on Uniprocessor Systems
		whatisRCU.txt

Documentation/RCU/trace.txt

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+413 −0

Original line number	Diff line number	Diff line
		CONFIG_RCU_TRACE debugfs Files and Formats


		The rcupreempt and rcutree implementations of RCU provide debugfs trace
		output that summarizes counters and state. This information is useful for
		debugging RCU itself, and can sometimes also help to debug abuses of RCU.
		Note that the rcuclassic implementation of RCU does not provide debugfs
		trace output.

		The following sections describe the debugfs files and formats for
		preemptable RCU (rcupreempt) and hierarchical RCU (rcutree).


		Preemptable RCU debugfs Files and Formats

		This implementation of RCU provides three debugfs files under the
		top-level directory RCU: rcu/rcuctrs (which displays the per-CPU
		counters used by preemptable RCU) rcu/rcugp (which displays grace-period
		counters), and rcu/rcustats (which internal counters for debugging RCU).

		The output of "cat rcu/rcuctrs" looks as follows:

		CPU last cur F M
		0 5 -5 0 0
		1 -1 0 0 0
		2 0 1 0 0
		3 0 1 0 0
		4 0 1 0 0
		5 0 1 0 0
		6 0 2 0 0
		7 0 -1 0 0
		8 0 1 0 0
		ggp = 26226, state = waitzero

		The per-CPU fields are as follows:

		o "CPU" gives the CPU number. Offline CPUs are not displayed.

		o "last" gives the value of the counter that is being decremented
		for the current grace period phase. In the example above,
		the counters sum to 4, indicating that there are still four
		RCU read-side critical sections still running that started
		before the last counter flip.

		o "cur" gives the value of the counter that is currently being
		both incremented (by rcu_read_lock()) and decremented (by
		rcu_read_unlock()). In the example above, the counters sum to
		1, indicating that there is only one RCU read-side critical section
		still running that started after the last counter flip.

		o "F" indicates whether RCU is waiting for this CPU to acknowledge
		a counter flip. In the above example, RCU is not waiting on any,
		which is consistent with the state being "waitzero" rather than
		"waitack".

		o "M" indicates whether RCU is waiting for this CPU to execute a
		memory barrier. In the above example, RCU is not waiting on any,
		which is consistent with the state being "waitzero" rather than
		"waitmb".

		o "ggp" is the global grace-period counter.

		o "state" is the RCU state, which can be one of the following:

		o "idle": there is no grace period in progress.

		o "waitack": RCU just incremented the global grace-period
		counter, which has the effect of reversing the roles of
		the "last" and "cur" counters above, and is waiting for
		all the CPUs to acknowledge the flip. Once the flip has
		been acknowledged, CPUs will no longer be incrementing
		what are now the "last" counters, so that their sum will
		decrease monotonically down to zero.

		o "waitzero": RCU is waiting for the sum of the "last" counters
		to decrease to zero.

		o "waitmb": RCU is waiting for each CPU to execute a memory
		barrier, which ensures that instructions from a given CPU's
		last RCU read-side critical section cannot be reordered
		with instructions following the memory-barrier instruction.

		The output of "cat rcu/rcugp" looks as follows:

		oldggp=48870 newggp=48873

		Note that reading from this file provokes a synchronize_rcu(). The
		"oldggp" value is that of "ggp" from rcu/rcuctrs above, taken before
		executing the synchronize_rcu(), and the "newggp" value is also the
		"ggp" value, but taken after the synchronize_rcu() command returns.


		The output of "cat rcu/rcugp" looks as follows:

		na=1337955 nl=40 wa=1337915 wl=44 da=1337871 dl=0 dr=1337871 di=1337871
		1=50989 e1=6138 i1=49722 ie1=82 g1=49640 a1=315203 ae1=265563 a2=49640
		z1=1401244 ze1=1351605 z2=49639 m1=5661253 me1=5611614 m2=49639

		These are counters tracking internal preemptable-RCU events, however,
		some of them may be useful for debugging algorithms using RCU. In
		particular, the "nl", "wl", and "dl" values track the number of RCU
		callbacks in various states. The fields are as follows:

		o "na" is the total number of RCU callbacks that have been enqueued
		since boot.

		o "nl" is the number of RCU callbacks waiting for the previous
		grace period to end so that they can start waiting on the next
		grace period.

		o "wa" is the total number of RCU callbacks that have started waiting
		for a grace period since boot. "na" should be roughly equal to
		"nl" plus "wa".

		o "wl" is the number of RCU callbacks currently waiting for their
		grace period to end.

		o "da" is the total number of RCU callbacks whose grace periods
		have completed since boot. "wa" should be roughly equal to
		"wl" plus "da".

		o "dr" is the total number of RCU callbacks that have been removed
		from the list of callbacks ready to invoke. "dr" should be roughly
		equal to "da".

		o "di" is the total number of RCU callbacks that have been invoked
		since boot. "di" should be roughly equal to "da", though some
		early versions of preemptable RCU had a bug so that only the
		last CPU's count of invocations was displayed, rather than the
		sum of all CPU's counts.

		o "1" is the number of calls to rcu_try_flip(). This should be
		roughly equal to the sum of "e1", "i1", "a1", "z1", and "m1"
		described below. In other words, the number of times that
		the state machine is visited should be equal to the sum of the
		number of times that each state is visited plus the number of
		times that the state-machine lock acquisition failed.

		o "e1" is the number of times that rcu_try_flip() was unable to
		acquire the fliplock.

		o "i1" is the number of calls to rcu_try_flip_idle().

		o "ie1" is the number of times rcu_try_flip_idle() exited early
		due to the calling CPU having no work for RCU.

		o "g1" is the number of times that rcu_try_flip_idle() decided
		to start a new grace period. "i1" should be roughly equal to
		"ie1" plus "g1".

		o "a1" is the number of calls to rcu_try_flip_waitack().

		o "ae1" is the number of times that rcu_try_flip_waitack() found
		that at least one CPU had not yet acknowledge the new grace period
		(AKA "counter flip").

		o "a2" is the number of time rcu_try_flip_waitack() found that
		all CPUs had acknowledged. "a1" should be roughly equal to
		"ae1" plus "a2". (This particular output was collected on
		a 128-CPU machine, hence the smaller-than-usual fraction of
		calls to rcu_try_flip_waitack() finding all CPUs having already
		acknowledged.)

		o "z1" is the number of calls to rcu_try_flip_waitzero().

		o "ze1" is the number of times that rcu_try_flip_waitzero() found
		that not all of the old RCU read-side critical sections had
		completed.

		o "z2" is the number of times that rcu_try_flip_waitzero() finds
		the sum of the counters equal to zero, in other words, that
		all of the old RCU read-side critical sections had completed.
		The value of "z1" should be roughly equal to "ze1" plus
		"z2".

		o "m1" is the number of calls to rcu_try_flip_waitmb().

		o "me1" is the number of times that rcu_try_flip_waitmb() finds
		that at least one CPU has not yet executed a memory barrier.

		o "m2" is the number of times that rcu_try_flip_waitmb() finds that
		all CPUs have executed a memory barrier.


		Hierarchical RCU debugfs Files and Formats

		This implementation of RCU provides three debugfs files under the
		top-level directory RCU: rcu/rcudata (which displays fields in struct
		rcu_data), rcu/rcugp (which displays grace-period counters), and
		rcu/rcuhier (which displays the struct rcu_node hierarchy).

		The output of "cat rcu/rcudata" looks as follows:

		rcu:
		0 c=4011 g=4012 pq=1 pqc=4011 qp=0 rpfq=1 rp=3c2a dt=23301/73 dn=2 df=1882 of=0 ri=2126 ql=2 b=10
		1 c=4011 g=4012 pq=1 pqc=4011 qp=0 rpfq=3 rp=39a6 dt=78073/1 dn=2 df=1402 of=0 ri=1875 ql=46 b=10
		2 c=4010 g=4010 pq=1 pqc=4010 qp=0 rpfq=-5 rp=1d12 dt=16646/0 dn=2 df=3140 of=0 ri=2080 ql=0 b=10
		3 c=4012 g=4013 pq=1 pqc=4012 qp=1 rpfq=3 rp=2b50 dt=21159/1 dn=2 df=2230 of=0 ri=1923 ql=72 b=10
		4 c=4012 g=4013 pq=1 pqc=4012 qp=1 rpfq=3 rp=1644 dt=5783/1 dn=2 df=3348 of=0 ri=2805 ql=7 b=10
		5 c=4012 g=4013 pq=0 pqc=4011 qp=1 rpfq=3 rp=1aac dt=5879/1 dn=2 df=3140 of=0 ri=2066 ql=10 b=10
		6 c=4012 g=4013 pq=1 pqc=4012 qp=1 rpfq=3 rp=ed8 dt=5847/1 dn=2 df=3797 of=0 ri=1266 ql=10 b=10
		7 c=4012 g=4013 pq=1 pqc=4012 qp=1 rpfq=3 rp=1fa2 dt=6199/1 dn=2 df=2795 of=0 ri=2162 ql=28 b=10
		rcu_bh:
		0 c=-268 g=-268 pq=1 pqc=-268 qp=0 rpfq=-145 rp=21d6 dt=23301/73 dn=2 df=0 of=0 ri=0 ql=0 b=10
		1 c=-268 g=-268 pq=1 pqc=-268 qp=1 rpfq=-170 rp=20ce dt=78073/1 dn=2 df=26 of=0 ri=5 ql=0 b=10
		2 c=-268 g=-268 pq=1 pqc=-268 qp=1 rpfq=-83 rp=fbd dt=16646/0 dn=2 df=28 of=0 ri=4 ql=0 b=10
		3 c=-268 g=-268 pq=1 pqc=-268 qp=0 rpfq=-105 rp=178c dt=21159/1 dn=2 df=28 of=0 ri=2 ql=0 b=10
		4 c=-268 g=-268 pq=1 pqc=-268 qp=1 rpfq=-30 rp=b54 dt=5783/1 dn=2 df=32 of=0 ri=0 ql=0 b=10
		5 c=-268 g=-268 pq=1 pqc=-268 qp=1 rpfq=-29 rp=df5 dt=5879/1 dn=2 df=30 of=0 ri=3 ql=0 b=10
		6 c=-268 g=-268 pq=1 pqc=-268 qp=1 rpfq=-28 rp=788 dt=5847/1 dn=2 df=32 of=0 ri=0 ql=0 b=10
		7 c=-268 g=-268 pq=1 pqc=-268 qp=1 rpfq=-53 rp=1098 dt=6199/1 dn=2 df=30 of=0 ri=3 ql=0 b=10

		The first section lists the rcu_data structures for rcu, the second for
		rcu_bh. Each section has one line per CPU, or eight for this 8-CPU system.
		The fields are as follows:

		o The number at the beginning of each line is the CPU number.
		CPUs numbers followed by an exclamation mark are offline,
		but have been online at least once since boot. There will be
		no output for CPUs that have never been online, which can be
		a good thing in the surprisingly common case where NR_CPUS is
		substantially larger than the number of actual CPUs.

		o "c" is the count of grace periods that this CPU believes have
		completed. CPUs in dynticks idle mode may lag quite a ways
		behind, for example, CPU 4 under "rcu" above, which has slept
		through the past 25 RCU grace periods. It is not unusual to
		see CPUs lagging by thousands of grace periods.

		o "g" is the count of grace periods that this CPU believes have
		started. Again, CPUs in dynticks idle mode may lag behind.
		If the "c" and "g" values are equal, this CPU has already
		reported a quiescent state for the last RCU grace period that
		it is aware of, otherwise, the CPU believes that it owes RCU a
		quiescent state.

		o "pq" indicates that this CPU has passed through a quiescent state
		for the current grace period. It is possible for "pq" to be
		"1" and "c" different than "g", which indicates that although
		the CPU has passed through a quiescent state, either (1) this
		CPU has not yet reported that fact, (2) some other CPU has not
		yet reported for this grace period, or (3) both.

		o "pqc" indicates which grace period the last-observed quiescent
		state for this CPU corresponds to. This is important for handling
		the race between CPU 0 reporting an extended dynticks-idle
		quiescent state for CPU 1 and CPU 1 suddenly waking up and
		reporting its own quiescent state. If CPU 1 was the last CPU
		for the current grace period, then the CPU that loses this race
		will attempt to incorrectly mark CPU 1 as having checked in for
		the next grace period!

		o "qp" indicates that RCU still expects a quiescent state from
		this CPU.

		o "rpfq" is the number of rcu_pending() calls on this CPU required
		to induce this CPU to invoke force_quiescent_state().

		o "rp" is low-order four hex digits of the count of how many times
		rcu_pending() has been invoked on this CPU.

		o "dt" is the current value of the dyntick counter that is incremented
		when entering or leaving dynticks idle state, either by the
		scheduler or by irq. The number after the "/" is the interrupt
		nesting depth when in dyntick-idle state, or one greater than
		the interrupt-nesting depth otherwise.

		This field is displayed only for CONFIG_NO_HZ kernels.

		o "dn" is the current value of the dyntick counter that is incremented
		when entering or leaving dynticks idle state via NMI. If both
		the "dt" and "dn" values are even, then this CPU is in dynticks
		idle mode and may be ignored by RCU. If either of these two
		counters is odd, then RCU must be alert to the possibility of
		an RCU read-side critical section running on this CPU.

		This field is displayed only for CONFIG_NO_HZ kernels.

		o "df" is the number of times that some other CPU has forced a
		quiescent state on behalf of this CPU due to this CPU being in
		dynticks-idle state.

		This field is displayed only for CONFIG_NO_HZ kernels.

		o "of" is the number of times that some other CPU has forced a
		quiescent state on behalf of this CPU due to this CPU being
		offline. In a perfect world, this might neve happen, but it
		turns out that offlining and onlining a CPU can take several grace
		periods, and so there is likely to be an extended period of time
		when RCU believes that the CPU is online when it really is not.
		Please note that erring in the other direction (RCU believing a
		CPU is offline when it is really alive and kicking) is a fatal
		error, so it makes sense to err conservatively.

		o "ri" is the number of times that RCU has seen fit to send a
		reschedule IPI to this CPU in order to get it to report a
		quiescent state.

		o "ql" is the number of RCU callbacks currently residing on
		this CPU. This is the total number of callbacks, regardless
		of what state they are in (new, waiting for grace period to
		start, waiting for grace period to end, ready to invoke).

		o "b" is the batch limit for this CPU. If more than this number
		of RCU callbacks is ready to invoke, then the remainder will
		be deferred.


		The output of "cat rcu/rcugp" looks as follows:

		rcu: completed=33062 gpnum=33063
		rcu_bh: completed=464 gpnum=464

		Again, this output is for both "rcu" and "rcu_bh". The fields are
		taken from the rcu_state structure, and are as follows:

		o "completed" is the number of grace periods that have completed.
		It is comparable to the "c" field from rcu/rcudata in that a
		CPU whose "c" field matches the value of "completed" is aware
		that the corresponding RCU grace period has completed.

		o "gpnum" is the number of grace periods that have started. It is
		comparable to the "g" field from rcu/rcudata in that a CPU
		whose "g" field matches the value of "gpnum" is aware that the
		corresponding RCU grace period has started.

		If these two fields are equal (as they are for "rcu_bh" above),
		then there is no grace period in progress, in other words, RCU
		is idle. On the other hand, if the two fields differ (as they
		do for "rcu" above), then an RCU grace period is in progress.


		The output of "cat rcu/rcuhier" looks as follows, with very long lines:

		c=6902 g=6903 s=2 jfq=3 j=72c7 nfqs=13142/nfqsng=0(13142) fqlh=6
		1/1 0:127 ^0
		3/3 0:35 ^0 0/0 36:71 ^1 0/0 72:107 ^2 0/0 108:127 ^3
		3/3f 0:5 ^0 2/3 6:11 ^1 0/0 12:17 ^2 0/0 18:23 ^3 0/0 24:29 ^4 0/0 30:35 ^5 0/0 36:41 ^0 0/0 42:47 ^1 0/0 48:53 ^2 0/0 54:59 ^3 0/0 60:65 ^4 0/0 66:71 ^5 0/0 72:77 ^0 0/0 78:83 ^1 0/0 84:89 ^2 0/0 90:95 ^3 0/0 96:101 ^4 0/0 102:107 ^5 0/0 108:113 ^0 0/0 114:119 ^1 0/0 120:125 ^2 0/0 126:127 ^3
		rcu_bh:
		c=-226 g=-226 s=1 jfq=-5701 j=72c7 nfqs=88/nfqsng=0(88) fqlh=0
		0/1 0:127 ^0
		0/3 0:35 ^0 0/0 36:71 ^1 0/0 72:107 ^2 0/0 108:127 ^3
		0/3f 0:5 ^0 0/3 6:11 ^1 0/0 12:17 ^2 0/0 18:23 ^3 0/0 24:29 ^4 0/0 30:35 ^5 0/0 36:41 ^0 0/0 42:47 ^1 0/0 48:53 ^2 0/0 54:59 ^3 0/0 60:65 ^4 0/0 66:71 ^5 0/0 72:77 ^0 0/0 78:83 ^1 0/0 84:89 ^2 0/0 90:95 ^3 0/0 96:101 ^4 0/0 102:107 ^5 0/0 108:113 ^0 0/0 114:119 ^1 0/0 120:125 ^2 0/0 126:127 ^3

		This is once again split into "rcu" and "rcu_bh" portions. The fields are
		as follows:

		o "c" is exactly the same as "completed" under rcu/rcugp.

		o "g" is exactly the same as "gpnum" under rcu/rcugp.

		o "s" is the "signaled" state that drives force_quiescent_state()'s
		state machine.

		o "jfq" is the number of jiffies remaining for this grace period
		before force_quiescent_state() is invoked to help push things
		along. Note that CPUs in dyntick-idle mode thoughout the grace
		period will not report on their own, but rather must be check by
		some other CPU via force_quiescent_state().

		o "j" is the low-order four hex digits of the jiffies counter.
		Yes, Paul did run into a number of problems that turned out to
		be due to the jiffies counter no longer counting. Why do you ask?

		o "nfqs" is the number of calls to force_quiescent_state() since
		boot.

		o "nfqsng" is the number of useless calls to force_quiescent_state(),
		where there wasn't actually a grace period active. This can
		happen due to races. The number in parentheses is the difference
		between "nfqs" and "nfqsng", or the number of times that
		force_quiescent_state() actually did some real work.

		o "fqlh" is the number of calls to force_quiescent_state() that
		exited immediately (without even being counted in nfqs above)
		due to contention on ->fqslock.

		o Each element of the form "1/1 0:127 ^0" represents one struct
		rcu_node. Each line represents one level of the hierarchy, from
		root to leaves. It is best to think of the rcu_data structures
		as forming yet another level after the leaves. Note that there
		might be either one, two, or three levels of rcu_node structures,
		depending on the relationship between CONFIG_RCU_FANOUT and
		CONFIG_NR_CPUS.

		o The numbers separated by the "/" are the qsmask followed
		by the qsmaskinit. The qsmask will have one bit
		set for each entity in the next lower level that
		has not yet checked in for the current grace period.
		The qsmaskinit will have one bit for each entity that is
		currently expected to check in during each grace period.
		The value of qsmaskinit is assigned to that of qsmask
		at the beginning of each grace period.

		For example, for "rcu", the qsmask of the first entry
		of the lowest level is 0x14, meaning that we are still
		waiting for CPUs 2 and 4 to check in for the current
		grace period.

		o The numbers separated by the ":" are the range of CPUs
		served by this struct rcu_node. This can be helpful
		in working out how the hierarchy is wired together.

		For example, the first entry at the lowest level shows
		"0:5", indicating that it covers CPUs 0 through 5.

		o The number after the "^" indicates the bit in the
		next higher level rcu_node structure that this
		rcu_node structure corresponds to.

		For example, the first entry at the lowest level shows
		"^0", indicating that it corresponds to bit zero in
		the first entry at the middle level.

Documentation/lockstat.txt

+33 −18

Original line number	Diff line number	Diff line
		@@ -71,35 +71,50 @@ Look at the current lock statistics:

		# less /proc/lock_stat

		01 lock_stat version 0.2
		01 lock_stat version 0.3
		02 -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
		03 class name con-bounces contentions waittime-min waittime-max waittime-total acq-bounces acquisitions holdtime-min holdtime-max holdtime-total
		04 -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
		05
		06 &inode->i_data.tree_lock-W: 15 21657 0.18 1093295.30 11547131054.85 58 10415 0.16 87.51 6387.60
		07 &inode->i_data.tree_lock-R: 0 0 0.00 0.00 0.00 23302 231198 0.25 8.45 98023.38
		08 --------------------------
		09 &inode->i_data.tree_lock 0 [<ffffffff8027c08f>] add_to_page_cache+0x5f/0x190
		10
		11 ...............................................................................................................................................................................................
		12
		13 dcache_lock: 1037 1161 0.38 45.32 774.51 6611 243371 0.15 306.48 77387.24
		14 -----------
		15 dcache_lock 180 [<ffffffff802c0d7e>] sys_getcwd+0x11e/0x230
		16 dcache_lock 165 [<ffffffff802c002a>] d_alloc+0x15a/0x210
		17 dcache_lock 33 [<ffffffff8035818d>] _atomic_dec_and_lock+0x4d/0x70
		18 dcache_lock 1 [<ffffffff802beef8>] shrink_dcache_parent+0x18/0x130
		06 &mm->mmap_sem-W: 233 538 18446744073708 22924.27 607243.51 1342 45806 1.71 8595.89 1180582.34
		07 &mm->mmap_sem-R: 205 587 18446744073708 28403.36 731975.00 1940 412426 0.58 187825.45 6307502.88
		08 ---------------
		09 &mm->mmap_sem 487 [<ffffffff8053491f>] do_page_fault+0x466/0x928
		10 &mm->mmap_sem 179 [<ffffffff802a6200>] sys_mprotect+0xcd/0x21d
		11 &mm->mmap_sem 279 [<ffffffff80210a57>] sys_mmap+0x75/0xce
		12 &mm->mmap_sem 76 [<ffffffff802a490b>] sys_munmap+0x32/0x59
		13 ---------------
		14 &mm->mmap_sem 270 [<ffffffff80210a57>] sys_mmap+0x75/0xce
		15 &mm->mmap_sem 431 [<ffffffff8053491f>] do_page_fault+0x466/0x928
		16 &mm->mmap_sem 138 [<ffffffff802a490b>] sys_munmap+0x32/0x59
		17 &mm->mmap_sem 145 [<ffffffff802a6200>] sys_mprotect+0xcd/0x21d
		18
		19 ...............................................................................................................................................................................................
		20
		21 dcache_lock: 621 623 0.52 118.26 1053.02 6745 91930 0.29 316.29 118423.41
		22 -----------
		23 dcache_lock 179 [<ffffffff80378274>] _atomic_dec_and_lock+0x34/0x54
		24 dcache_lock 113 [<ffffffff802cc17b>] d_alloc+0x19a/0x1eb
		25 dcache_lock 99 [<ffffffff802ca0dc>] d_rehash+0x1b/0x44
		26 dcache_lock 104 [<ffffffff802cbca0>] d_instantiate+0x36/0x8a
		27 -----------
		28 dcache_lock 192 [<ffffffff80378274>] _atomic_dec_and_lock+0x34/0x54
		29 dcache_lock 98 [<ffffffff802ca0dc>] d_rehash+0x1b/0x44
		30 dcache_lock 72 [<ffffffff802cc17b>] d_alloc+0x19a/0x1eb
		31 dcache_lock 112 [<ffffffff802cbca0>] d_instantiate+0x36/0x8a

		This excerpt shows the first two lock class statistics. Line 01 shows the
		output version - each time the format changes this will be updated. Line 02-04
		show the header with column descriptions. Lines 05-10 and 13-18 show the actual
		show the header with column descriptions. Lines 05-18 and 20-31 show the actual
		statistics. These statistics come in two parts; the actual stats separated by a
		short separator (line 08, 14) from the contention points.
		short separator (line 08, 13) from the contention points.

		The first lock (05-10) is a read/write lock, and shows two lines above the
		The first lock (05-18) is a read/write lock, and shows two lines above the
		short separator. The contention points don't match the column descriptors,
		they have two: contentions and [<IP>] symbol.
		they have two: contentions and [<IP>] symbol. The second set of contention
		points are the points we're contending with.

		The integer part of the time values is in us.

		View the top contending locks:

arch/powerpc/platforms/pseries/rtasd.c

+4 −0

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arch/um/include/asm/system.h

+7 −7

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