Commit e3aa52d6 authored by Avi Kivity's avatar Avi Kivity
Browse files

Merge commit '29ce8310' into next 



* commit '29ce8310': (34 commits)
  rcu: provide rcu_virt_note_context_switch() function.
  rcu: get rid of signed overflow in check_cpu_stall()
  rcu: optimize rcutiny
  rcu: prevent call_rcu() from diving into rcu core if irqs disabled
  rcu: further lower priority in rcu_yield()
  rcu: introduce kfree_rcu()
  rcu: fix spelling
  rcu: call __rcu_read_unlock() in exit_rcu for tree RCU
  rcu: Converge TINY_RCU expedited and normal boosting
  rcu: remove useless ->boosted_this_gp field
  rcu: code cleanups in TINY_RCU priority boosting.
  rcu: Switch to this_cpu() primitives
  rcu: Use WARN_ON_ONCE for DEBUG_OBJECTS_RCU_HEAD warnings
  rcu: mark rcutorture boosting callback as being on-stack
  rcu: add DEBUG_OBJECTS_RCU_HEAD check for alignment
  rcu: Enable DEBUG_OBJECTS_RCU_HEAD from !PREEMPT
  rcu: Add forward-progress diagnostic for per-CPU kthreads
  rcu: add grace-period age and more kthread state to tracing
  rcu: fix tracing bug thinko on boost-balk attribution
  rcu: update tracing documentation for new rcutorture and rcuboost
  ...

Pulling in rcu_virt_note_context_switch().

Signed-off-by: default avatarAvi Kivity <avi@redhat.com>

* commit '29ce8310': (34 commits)
  rcu: provide rcu_virt_note_context_switch() function.
  rcu: get rid of signed overflow in check_cpu_stall()
  rcu: optimize rcutiny
  rcu: prevent call_rcu() from diving into rcu core if irqs disabled
  rcu: further lower priority in rcu_yield()
  rcu: introduce kfree_rcu()
  rcu: fix spelling
  rcu: call __rcu_read_unlock() in exit_rcu for tree RCU
  rcu: Converge TINY_RCU expedited and normal boosting
  rcu: remove useless ->boosted_this_gp field
  rcu: code cleanups in TINY_RCU priority boosting.
  rcu: Switch to this_cpu() primitives
  rcu: Use WARN_ON_ONCE for DEBUG_OBJECTS_RCU_HEAD warnings
  rcu: mark rcutorture boosting callback as being on-stack
  rcu: add DEBUG_OBJECTS_RCU_HEAD check for alignment
  rcu: Enable DEBUG_OBJECTS_RCU_HEAD from !PREEMPT
  rcu: Add forward-progress diagnostic for per-CPU kthreads
  rcu: add grace-period age and more kthread state to tracing
  rcu: fix tracing bug thinko on boost-balk attribution
  rcu: update tracing documentation for new rcutorture and rcuboost
  ...
parents d2f62766 29ce8310

Documentation/RCU/00-INDEX

+1 −1
Original line number Diff line number Diff line
@@ -21,7 +21,7 @@ rcu.txt 
RTFP.txt

	- List of RCU papers (bibliography) going back to 1980.

stallwarn.txt

	- RCU CPU stall warnings (CONFIG_RCU_CPU_STALL_DETECTOR)

	- RCU CPU stall warnings (module parameter rcu_cpu_stall_suppress)

torture.txt

	- RCU Torture Test Operation (CONFIG_RCU_TORTURE_TEST)

trace.txt

Documentation/RCU/stallwarn.txt

+13 −10
Original line number Diff line number Diff line 
Using RCU's CPU Stall Detector



The CONFIG_RCU_CPU_STALL_DETECTOR kernel config parameter enables

RCU's CPU stall detector, which detects conditions that unduly delay

RCU grace periods.  The stall detector's idea of what constitutes

"unduly delayed" is controlled by a set of C preprocessor macros:

The rcu_cpu_stall_suppress module parameter enables RCU's CPU stall

detector, which detects conditions that unduly delay RCU grace periods.

This module parameter enables CPU stall detection by default, but

may be overridden via boot-time parameter or at runtime via sysfs.

The stall detector's idea of what constitutes "unduly delayed" is

controlled by a set of kernel configuration variables and cpp macros:



RCU_SECONDS_TILL_STALL_CHECK

CONFIG_RCU_CPU_STALL_TIMEOUT



	This macro defines the period of time that RCU will wait from

	the beginning of a grace period until it issues an RCU CPU

	stall warning.	This time period is normally ten seconds.

	This kernel configuration parameter defines the period of time

	that RCU will wait from the beginning of a grace period until it

	issues an RCU CPU stall warning.  This time period is normally

	ten seconds.



RCU_SECONDS_TILL_STALL_RECHECK



	This macro defines the period of time that RCU will wait after

	issuing a stall warning until it issues another stall warning

	for the same stall.  This time period is normally set to thirty

	seconds.

	for the same stall.  This time period is normally set to three

	times the check interval plus thirty seconds.



RCU_STALL_RAT_DELAY

Documentation/RCU/trace.txt

+236 −59
Original line number Diff line number Diff line
@@ -10,34 +10,46 @@ for rcutree and next for rcutiny. 


CONFIG_TREE_RCU and CONFIG_TREE_PREEMPT_RCU debugfs Files and Formats



These implementations of RCU provides five debugfs files under the

top-level directory RCU: rcu/rcudata (which displays fields in struct

rcu_data), rcu/rcudata.csv (which is a .csv spreadsheet version of

rcu/rcudata), rcu/rcugp (which displays grace-period counters),

rcu/rcuhier (which displays the struct rcu_node hierarchy), and

rcu/rcu_pending (which displays counts of the reasons that the

rcu_pending() function decided that there was core RCU work to do).

These implementations of RCU provides several debugfs files under the

top-level directory "rcu":



rcu/rcudata:

	Displays fields in struct rcu_data.

rcu/rcudata.csv:

	Comma-separated values spreadsheet version of rcudata.

rcu/rcugp:

	Displays grace-period counters.

rcu/rcuhier:

	Displays the struct rcu_node hierarchy.

rcu/rcu_pending:

	Displays counts of the reasons rcu_pending() decided that RCU had

	work to do.

rcu/rcutorture:

	Displays rcutorture test progress.

rcu/rcuboost:

	Displays RCU boosting statistics.  Only present if

	CONFIG_RCU_BOOST=y.



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



rcu_sched:

  0 c=17829 g=17829 pq=1 pqc=17829 qp=0 dt=10951/1 dn=0 df=1101 of=0 ri=36 ql=0 b=10

  1 c=17829 g=17829 pq=1 pqc=17829 qp=0 dt=16117/1 dn=0 df=1015 of=0 ri=0 ql=0 b=10

  2 c=17829 g=17829 pq=1 pqc=17829 qp=0 dt=1445/1 dn=0 df=1839 of=0 ri=0 ql=0 b=10

  3 c=17829 g=17829 pq=1 pqc=17829 qp=0 dt=6681/1 dn=0 df=1545 of=0 ri=0 ql=0 b=10

  4 c=17829 g=17829 pq=1 pqc=17829 qp=0 dt=1003/1 dn=0 df=1992 of=0 ri=0 ql=0 b=10

  5 c=17829 g=17830 pq=1 pqc=17829 qp=1 dt=3887/1 dn=0 df=3331 of=0 ri=4 ql=2 b=10

  6 c=17829 g=17829 pq=1 pqc=17829 qp=0 dt=859/1 dn=0 df=3224 of=0 ri=0 ql=0 b=10

  7 c=17829 g=17830 pq=0 pqc=17829 qp=1 dt=3761/1 dn=0 df=1818 of=0 ri=0 ql=2 b=10

  0 c=20972 g=20973 pq=1 pqc=20972 qp=0 dt=545/1/0 df=50 of=0 ri=0 ql=163 qs=NRW. kt=0/W/0 ktl=ebc3 b=10 ci=153737 co=0 ca=0

  1 c=20972 g=20973 pq=1 pqc=20972 qp=0 dt=967/1/0 df=58 of=0 ri=0 ql=634 qs=NRW. kt=0/W/1 ktl=58c b=10 ci=191037 co=0 ca=0

  2 c=20972 g=20973 pq=1 pqc=20972 qp=0 dt=1081/1/0 df=175 of=0 ri=0 ql=74 qs=N.W. kt=0/W/2 ktl=da94 b=10 ci=75991 co=0 ca=0

  3 c=20942 g=20943 pq=1 pqc=20942 qp=1 dt=1846/0/0 df=404 of=0 ri=0 ql=0 qs=.... kt=0/W/3 ktl=d1cd b=10 ci=72261 co=0 ca=0

  4 c=20972 g=20973 pq=1 pqc=20972 qp=0 dt=369/1/0 df=83 of=0 ri=0 ql=48 qs=N.W. kt=0/W/4 ktl=e0e7 b=10 ci=128365 co=0 ca=0

  5 c=20972 g=20973 pq=1 pqc=20972 qp=0 dt=381/1/0 df=64 of=0 ri=0 ql=169 qs=NRW. kt=0/W/5 ktl=fb2f b=10 ci=164360 co=0 ca=0

  6 c=20972 g=20973 pq=1 pqc=20972 qp=0 dt=1037/1/0 df=183 of=0 ri=0 ql=62 qs=N.W. kt=0/W/6 ktl=d2ad b=10 ci=65663 co=0 ca=0

  7 c=20897 g=20897 pq=1 pqc=20896 qp=0 dt=1572/0/0 df=382 of=0 ri=0 ql=0 qs=.... kt=0/W/7 ktl=cf15 b=10 ci=75006 co=0 ca=0

rcu_bh:

  0 c=-275 g=-275 pq=1 pqc=-275 qp=0 dt=10951/1 dn=0 df=0 of=0 ri=0 ql=0 b=10

  1 c=-275 g=-275 pq=1 pqc=-275 qp=0 dt=16117/1 dn=0 df=13 of=0 ri=0 ql=0 b=10

  2 c=-275 g=-275 pq=1 pqc=-275 qp=0 dt=1445/1 dn=0 df=15 of=0 ri=0 ql=0 b=10

  3 c=-275 g=-275 pq=1 pqc=-275 qp=0 dt=6681/1 dn=0 df=9 of=0 ri=0 ql=0 b=10

  4 c=-275 g=-275 pq=1 pqc=-275 qp=0 dt=1003/1 dn=0 df=15 of=0 ri=0 ql=0 b=10

  5 c=-275 g=-275 pq=1 pqc=-275 qp=0 dt=3887/1 dn=0 df=15 of=0 ri=0 ql=0 b=10

  6 c=-275 g=-275 pq=1 pqc=-275 qp=0 dt=859/1 dn=0 df=15 of=0 ri=0 ql=0 b=10

  7 c=-275 g=-275 pq=1 pqc=-275 qp=0 dt=3761/1 dn=0 df=15 of=0 ri=0 ql=0 b=10

  0 c=1480 g=1480 pq=1 pqc=1479 qp=0 dt=545/1/0 df=6 of=0 ri=1 ql=0 qs=.... kt=0/W/0 ktl=ebc3 b=10 ci=0 co=0 ca=0

  1 c=1480 g=1480 pq=1 pqc=1479 qp=0 dt=967/1/0 df=3 of=0 ri=1 ql=0 qs=.... kt=0/W/1 ktl=58c b=10 ci=151 co=0 ca=0

  2 c=1480 g=1480 pq=1 pqc=1479 qp=0 dt=1081/1/0 df=6 of=0 ri=1 ql=0 qs=.... kt=0/W/2 ktl=da94 b=10 ci=0 co=0 ca=0

  3 c=1480 g=1480 pq=1 pqc=1479 qp=0 dt=1846/0/0 df=8 of=0 ri=1 ql=0 qs=.... kt=0/W/3 ktl=d1cd b=10 ci=0 co=0 ca=0

  4 c=1480 g=1480 pq=1 pqc=1479 qp=0 dt=369/1/0 df=6 of=0 ri=1 ql=0 qs=.... kt=0/W/4 ktl=e0e7 b=10 ci=0 co=0 ca=0

  5 c=1480 g=1480 pq=1 pqc=1479 qp=0 dt=381/1/0 df=4 of=0 ri=1 ql=0 qs=.... kt=0/W/5 ktl=fb2f b=10 ci=0 co=0 ca=0

  6 c=1480 g=1480 pq=1 pqc=1479 qp=0 dt=1037/1/0 df=6 of=0 ri=1 ql=0 qs=.... kt=0/W/6 ktl=d2ad b=10 ci=0 co=0 ca=0

  7 c=1474 g=1474 pq=1 pqc=1473 qp=0 dt=1572/0/0 df=8 of=0 ri=1 ql=0 qs=.... kt=0/W/7 ktl=cf15 b=10 ci=0 co=0 ca=0



The first section lists the rcu_data structures for rcu_sched, the second

for rcu_bh.  Note that CONFIG_TREE_PREEMPT_RCU kernels will have an
@@ -52,17 +64,18 @@ o The number at the beginning of each line is the CPU number. 
	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_sched" above, which has

	slept through the past 25 RCU grace periods.  It is not unusual

	to see CPUs lagging by thousands of grace periods.

	completed.  Offlined CPUs and CPUs in dynticks idle mode may

	lag quite a ways behind, for example, CPU 6 under "rcu_sched"

	above, which has been offline through not quite 40,000 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.

	started.  Again, offlined CPUs and 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
@@ -81,22 +94,16 @@ o "pqc" indicates which grace period the last-observed quiescent 
	the next grace period!



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

	this CPU.

	this CPU.  Offlined CPUs and CPUs in dyntick idle mode might

	well have qp=1, which is OK: RCU is still ignoring them.



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.

	scheduler or by irq.  This number is even if the CPU is in

	dyntick idle mode and odd otherwise.  The number after the first

	"/" is the interrupt nesting depth when in dyntick-idle state,

	or one greater than the interrupt-nesting depth otherwise.

	The number after the second "/" is the NMI nesting depth.



	This field is displayed only for CONFIG_NO_HZ kernels.
@@ -108,7 +115,7 @@ o "df" is the number of times that some other CPU has forced a 


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

	offline.  In a perfect world, this might never 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.
@@ -125,6 +132,62 @@ o "ql" is the number of RCU callbacks currently residing on 
	of what state they are in (new, waiting for grace period to

	start, waiting for grace period to end, ready to invoke).



o	"qs" gives an indication of the state of the callback queue

	with four characters:



	"N"	Indicates that there are callbacks queued that are not

		ready to be handled by the next grace period, and thus

		will be handled by the grace period following the next

		one.



	"R"	Indicates that there are callbacks queued that are

		ready to be handled by the next grace period.



	"W"	Indicates that there are callbacks queued that are

		waiting on the current grace period.



	"D"	Indicates that there are callbacks queued that have

		already been handled by a prior grace period, and are

		thus waiting to be invoked.  Note that callbacks in

		the process of being invoked are not counted here.

		Callbacks in the process of being invoked are those

		that have been removed from the rcu_data structures

		queues by rcu_do_batch(), but which have not yet been

		invoked.



	If there are no callbacks in a given one of the above states,

	the corresponding character is replaced by ".".



o	"kt" is the per-CPU kernel-thread state.  The digit preceding

	the first slash is zero if there is no work pending and 1

	otherwise.  The character between the first pair of slashes is

	as follows:



	"S"	The kernel thread is stopped, in other words, all

		CPUs corresponding to this rcu_node structure are

		offline.



	"R"	The kernel thread is running.



	"W"	The kernel thread is waiting because there is no work

		for it to do.



	"O"	The kernel thread is waiting because it has been

		forced off of its designated CPU or because its

		->cpus_allowed mask permits it to run on other than

		its designated CPU.



	"Y"	The kernel thread is yielding to avoid hogging CPU.



	"?"	Unknown value, indicates a bug.



	The number after the final slash is the CPU that the kthread

	is actually running on.



o	"ktl" is the low-order 16 bits (in hexadecimal) of the count of

	the number of times that this CPU's per-CPU kthread has gone

	through its loop servicing invoke_rcu_cpu_kthread() requests.



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.
@@ -174,14 +237,14 @@ o "gpnum" is the number of grace periods that have started. It is 
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    

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

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_sched" and "rcu_bh" portions,

and CONFIG_TREE_PREEMPT_RCU kernels will again have an additional
@@ -240,13 +303,20 @@ o Each element of the form "1/1 0:127 ^0" represents one struct 
		current grace period.



	o	The characters separated by the ">" indicate the state

		of the blocked-tasks lists.  A "T" preceding the ">"

		of the blocked-tasks lists.  A "G" preceding the ">"

		indicates that at least one task blocked in an RCU

		read-side critical section blocks the current grace

		period, while a "." preceding the ">" indicates otherwise.

		The character following the ">" indicates similarly for

		the next grace period.  A "T" should appear in this

		field only for rcu-preempt.

		period, while a "E" preceding the ">" indicates that

		at least one task blocked in an RCU read-side critical

		section blocks the current expedited grace period.

		A "T" character following the ">" indicates that at

		least one task is blocked within an RCU read-side

		critical section, regardless of whether any current

		grace period (expedited or normal) is inconvenienced.

		A "." character appears if the corresponding condition

		does not hold, so that "..>." indicates that no tasks

		are blocked.  In contrast, "GE>T" indicates maximal

		inconvenience from blocked tasks.



	o	The numbers separated by the ":" are the range of CPUs

		served by this struct rcu_node.  This can be helpful
@@ -328,6 +398,113 @@ o "nn" is the number of times that this CPU needed nothing. Alert 
	is due to short-circuit evaluation in rcu_pending().





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



rcutorture test sequence: 0 (test in progress)

rcutorture update version number: 615



The first line shows the number of rcutorture tests that have completed

since boot.  If a test is currently running, the "(test in progress)"

string will appear as shown above.  The second line shows the number of

update cycles that the current test has started, or zero if there is

no test in progress.





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



0:5 tasks=.... kt=W ntb=0 neb=0 nnb=0 j=2f95 bt=300f

     balk: nt=0 egt=989 bt=0 nb=0 ny=0 nos=16

6:7 tasks=.... kt=W ntb=0 neb=0 nnb=0 j=2f95 bt=300f

     balk: nt=0 egt=225 bt=0 nb=0 ny=0 nos=6



This information is output only for rcu_preempt.  Each two-line entry

corresponds to a leaf rcu_node strcuture.  The fields are as follows:



o	"n:m" is the CPU-number range for the corresponding two-line

	entry.  In the sample output above, the first entry covers

	CPUs zero through five and the second entry covers CPUs 6

	and 7.



o	"tasks=TNEB" gives the state of the various segments of the

	rnp->blocked_tasks list:



	"T"	This indicates that there are some tasks that blocked

		while running on one of the corresponding CPUs while

		in an RCU read-side critical section.



	"N"	This indicates that some of the blocked tasks are preventing

		the current normal (non-expedited) grace period from

		completing.



	"E"	This indicates that some of the blocked tasks are preventing

		the current expedited grace period from completing.



	"B"	This indicates that some of the blocked tasks are in

		need of RCU priority boosting.



	Each character is replaced with "." if the corresponding

	condition does not hold.



o	"kt" is the state of the RCU priority-boosting kernel

	thread associated with the corresponding rcu_node structure.

	The state can be one of the following:



	"S"	The kernel thread is stopped, in other words, all

		CPUs corresponding to this rcu_node structure are

		offline.



	"R"	The kernel thread is running.



	"W"	The kernel thread is waiting because there is no work

		for it to do.



	"Y"	The kernel thread is yielding to avoid hogging CPU.



	"?"	Unknown value, indicates a bug.



o	"ntb" is the number of tasks boosted.



o	"neb" is the number of tasks boosted in order to complete an

	expedited grace period.



o	"nnb" is the number of tasks boosted in order to complete a

	normal (non-expedited) grace period.  When boosting a task

	that was blocking both an expedited and a normal grace period,

	it is counted against the expedited total above.



o	"j" is the low-order 16 bits of the jiffies counter in

	hexadecimal.



o	"bt" is the low-order 16 bits of the value that the jiffies

	counter will have when we next start boosting, assuming that

	the current grace period does not end beforehand.  This is

	also in hexadecimal.



o	"balk: nt" counts the number of times we didn't boost (in

	other words, we balked) even though it was time to boost because

	there were no blocked tasks to boost.  This situation occurs

	when there is one blocked task on one rcu_node structure and

	none on some other rcu_node structure.



o	"egt" counts the number of times we balked because although

	there were blocked tasks, none of them were blocking the

	current grace period, whether expedited or otherwise.



o	"bt" counts the number of times we balked because boosting

	had already been initiated for the current grace period.



o	"nb" counts the number of times we balked because there

	was at least one task blocking the current non-expedited grace

	period that never had blocked.  If it is already running, it

	just won't help to boost its priority!



o	"ny" counts the number of times we balked because it was

	not yet time to start boosting.



o	"nos" counts the number of times we balked for other

	reasons, e.g., the grace period ended first.





CONFIG_TINY_RCU and CONFIG_TINY_PREEMPT_RCU debugfs Files and Formats



These implementations of RCU provides a single debugfs file under the
@@ -394,9 +571,9 @@ o "neb" is the number of expedited grace periods that have had 
o	"nnb" is the number of normal grace periods that have had

	to resort to RCU priority boosting since boot.



o	"j" is the low-order 12 bits of the jiffies counter in hexadecimal.

o	"j" is the low-order 16 bits of the jiffies counter in hexadecimal.



o	"bt" is the low-order 12 bits of the value that the jiffies counter

o	"bt" is the low-order 16 bits of the value that the jiffies counter

	will have at the next time that boosting is scheduled to begin.



o	In the line beginning with "normal balk", the fields are as follows:

Documentation/filesystems/proc.txt

+0 −1
Original line number Diff line number Diff line
@@ -836,7 +836,6 @@ Provides counts of softirq handlers serviced since boot time, for each cpu. 
 TASKLET:          0          0          0        290

   SCHED:      27035      26983      26971      26746

 HRTIMER:          0          0          0          0

     RCU:       1678       1769       2178       2250





1.3 IDE devices in /proc/ide

include/linux/interrupt.h

+0 −1
Original line number Diff line number Diff line
@@ -414,7 +414,6 @@ enum 
	TASKLET_SOFTIRQ,

	SCHED_SOFTIRQ,

	HRTIMER_SOFTIRQ,

	RCU_SOFTIRQ,	/* Preferable RCU should always be the last softirq */



	NR_SOFTIRQS

};

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