Commit 28142286 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull RCU changes from Ingo Molnar:
 "The main changes in this cycle were:

   - Improvements to expedited grace periods (Paul E McKenney)

   - Performance improvements to and locktorture tests for percpu-rwsem
     (Oleg Nesterov, Paul E McKenney)

   - Torture-test changes (Paul E McKenney, Davidlohr Bueso)

   - Documentation updates (Paul E McKenney)

   - Miscellaneous fixes (Paul E McKenney, Boqun Feng, Oleg Nesterov,
     Patrick Marlier)"

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (54 commits)
  fs/writeback, rcu: Don't use list_entry_rcu() for pointer offsetting in bdi_split_work_to_wbs()
  rcu: Better hotplug handling for synchronize_sched_expedited()
  rcu: Enable stall warnings for synchronize_rcu_expedited()
  rcu: Add tasks to expedited stall-warning messages
  rcu: Add online/offline info to expedited stall warning message
  rcu: Consolidate expedited CPU selection
  rcu: Prepare for consolidating expedited CPU selection
  cpu: Remove try_get_online_cpus()
  rcu: Stop excluding CPU hotplug in synchronize_sched_expedited()
  rcu: Stop silencing lockdep false positive for expedited grace periods
  rcu: Switch synchronize_sched_expedited() to IPI
  locktorture: Fix module unwind when bad torture_type specified
  torture: Forgive non-plural arguments
  rcutorture: Fix unused-function warning for torturing_tasks()
  rcutorture: Fix module unwind when bad torture_type specified
  rcu_sync: Cleanup the CONFIG_PROVE_RCU checks
  locking/percpu-rwsem: Clean up the lockdep annotations in percpu_down_read()
  locking/percpu-rwsem: Fix the comments outdated by rcu_sync
  locking/percpu-rwsem: Make use of the rcu_sync infrastructure
  locking/percpu-rwsem: Make percpu_free_rwsem() after kzalloc() safe
  ...
parents f5a8160c b33e18f6

Documentation/RCU/stallwarn.txt

+7 −0
Original line number Diff line number Diff line
@@ -205,6 +205,13 @@ o For !CONFIG_PREEMPT kernels, a CPU looping anywhere in the 
	behavior, you might need to replace some of the cond_resched()

	calls with calls to cond_resched_rcu_qs().



o	Booting Linux using a console connection that is too slow to

	keep up with the boot-time console-message rate.  For example,

	a 115Kbaud serial console can be -way- too slow to keep up

	with boot-time message rates, and will frequently result in

	RCU CPU stall warning messages.  Especially if you have added

	debug printk()s.



o	Anything that prevents RCU's grace-period kthreads from running.

	This can result in the "All QSes seen" console-log message.

	This message will include information on when the kthread last

Documentation/RCU/torture.txt

+13 −26
Original line number Diff line number Diff line
@@ -166,40 +166,27 @@ test_no_idle_hz Whether or not to test the ability of RCU to operate in 


torture_type	The type of RCU to test, with string values as follows:



		"rcu":  rcu_read_lock(), rcu_read_unlock() and call_rcu().



		"rcu_sync":  rcu_read_lock(), rcu_read_unlock(), and

			synchronize_rcu().



		"rcu_expedited": rcu_read_lock(), rcu_read_unlock(), and

			synchronize_rcu_expedited().

		"rcu":  rcu_read_lock(), rcu_read_unlock() and call_rcu(),

			along with expedited, synchronous, and polling

			variants.



		"rcu_bh": rcu_read_lock_bh(), rcu_read_unlock_bh(), and

			call_rcu_bh().



		"rcu_bh_sync": rcu_read_lock_bh(), rcu_read_unlock_bh(),

			and synchronize_rcu_bh().

			call_rcu_bh(), along with expedited and synchronous

			variants.



		"rcu_bh_expedited": rcu_read_lock_bh(), rcu_read_unlock_bh(),

			and synchronize_rcu_bh_expedited().

		"rcu_busted": This tests an intentionally incorrect version

			of RCU in order to help test rcutorture itself.



		"srcu": srcu_read_lock(), srcu_read_unlock() and

			call_srcu().



		"srcu_sync": srcu_read_lock(), srcu_read_unlock() and

			synchronize_srcu().



		"srcu_expedited": srcu_read_lock(), srcu_read_unlock() and

			synchronize_srcu_expedited().

			call_srcu(), along with expedited and

			synchronous variants.



		"sched": preempt_disable(), preempt_enable(), and

			call_rcu_sched().



		"sched_sync": preempt_disable(), preempt_enable(), and

			synchronize_sched().

			call_rcu_sched(), along with expedited,

			synchronous, and polling variants.



		"sched_expedited": preempt_disable(), preempt_enable(), and

			synchronize_sched_expedited().

		"tasks": voluntary context switch and call_rcu_tasks(),

			along with expedited and synchronous variants.



		Defaults to "rcu".

Documentation/RCU/trace.txt

+16 −16
Original line number Diff line number Diff line
@@ -56,14 +56,14 @@ rcuboost: 


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



  0!c=30455 g=30456 pq=1/0 qp=1 dt=126535/140000000000000/0 df=2002 of=4 ql=0/0 qs=N... b=10 ci=74572 nci=0 co=1131 ca=716

  1!c=30719 g=30720 pq=1/0 qp=0 dt=132007/140000000000000/0 df=1874 of=10 ql=0/0 qs=N... b=10 ci=123209 nci=0 co=685 ca=982

  2!c=30150 g=30151 pq=1/1 qp=1 dt=138537/140000000000000/0 df=1707 of=8 ql=0/0 qs=N... b=10 ci=80132 nci=0 co=1328 ca=1458

  3 c=31249 g=31250 pq=1/1 qp=0 dt=107255/140000000000000/0 df=1749 of=6 ql=0/450 qs=NRW. b=10 ci=151700 nci=0 co=509 ca=622

  4!c=29502 g=29503 pq=1/0 qp=1 dt=83647/140000000000000/0 df=965 of=5 ql=0/0 qs=N... b=10 ci=65643 nci=0 co=1373 ca=1521

  5 c=31201 g=31202 pq=1/0 qp=1 dt=70422/0/0 df=535 of=7 ql=0/0 qs=.... b=10 ci=58500 nci=0 co=764 ca=698

  6!c=30253 g=30254 pq=1/0 qp=1 dt=95363/140000000000000/0 df=780 of=5 ql=0/0 qs=N... b=10 ci=100607 nci=0 co=1414 ca=1353

  7 c=31178 g=31178 pq=1/0 qp=0 dt=91536/0/0 df=547 of=4 ql=0/0 qs=.... b=10 ci=109819 nci=0 co=1115 ca=969

  0!c=30455 g=30456 cnq=1/0:1 dt=126535/140000000000000/0 df=2002 of=4 ql=0/0 qs=N... b=10 ci=74572 nci=0 co=1131 ca=716

  1!c=30719 g=30720 cnq=1/0:0 dt=132007/140000000000000/0 df=1874 of=10 ql=0/0 qs=N... b=10 ci=123209 nci=0 co=685 ca=982

  2!c=30150 g=30151 cnq=1/1:1 dt=138537/140000000000000/0 df=1707 of=8 ql=0/0 qs=N... b=10 ci=80132 nci=0 co=1328 ca=1458

  3 c=31249 g=31250 cnq=1/1:0 dt=107255/140000000000000/0 df=1749 of=6 ql=0/450 qs=NRW. b=10 ci=151700 nci=0 co=509 ca=622

  4!c=29502 g=29503 cnq=1/0:1 dt=83647/140000000000000/0 df=965 of=5 ql=0/0 qs=N... b=10 ci=65643 nci=0 co=1373 ca=1521

  5 c=31201 g=31202 cnq=1/0:1 dt=70422/0/0 df=535 of=7 ql=0/0 qs=.... b=10 ci=58500 nci=0 co=764 ca=698

  6!c=30253 g=30254 cnq=1/0:1 dt=95363/140000000000000/0 df=780 of=5 ql=0/0 qs=N... b=10 ci=100607 nci=0 co=1414 ca=1353

  7 c=31178 g=31178 cnq=1/0:0 dt=91536/0/0 df=547 of=4 ql=0/0 qs=.... b=10 ci=109819 nci=0 co=1115 ca=969



This file has one line per CPU, or eight for this 8-CPU system.

The fields are as follows:
@@ -188,14 +188,14 @@ o "ca" is the number of RCU callbacks that have been adopted by this 
Kernels compiled with CONFIG_RCU_BOOST=y display the following from

/debug/rcu/rcu_preempt/rcudata:



  0!c=12865 g=12866 pq=1/0 qp=1 dt=83113/140000000000000/0 df=288 of=11 ql=0/0 qs=N... kt=0/O ktl=944 b=10 ci=60709 nci=0 co=748 ca=871

  1 c=14407 g=14408 pq=1/0 qp=0 dt=100679/140000000000000/0 df=378 of=7 ql=0/119 qs=NRW. kt=0/W ktl=9b6 b=10 ci=109740 nci=0 co=589 ca=485

  2 c=14407 g=14408 pq=1/0 qp=0 dt=105486/0/0 df=90 of=9 ql=0/89 qs=NRW. kt=0/W ktl=c0c b=10 ci=83113 nci=0 co=533 ca=490

  3 c=14407 g=14408 pq=1/0 qp=0 dt=107138/0/0 df=142 of=8 ql=0/188 qs=NRW. kt=0/W ktl=b96 b=10 ci=121114 nci=0 co=426 ca=290

  4 c=14405 g=14406 pq=1/0 qp=1 dt=50238/0/0 df=706 of=7 ql=0/0 qs=.... kt=0/W ktl=812 b=10 ci=34929 nci=0 co=643 ca=114

  5!c=14168 g=14169 pq=1/0 qp=0 dt=45465/140000000000000/0 df=161 of=11 ql=0/0 qs=N... kt=0/O ktl=b4d b=10 ci=47712 nci=0 co=677 ca=722

  6 c=14404 g=14405 pq=1/0 qp=0 dt=59454/0/0 df=94 of=6 ql=0/0 qs=.... kt=0/W ktl=e57 b=10 ci=55597 nci=0 co=701 ca=811

  7 c=14407 g=14408 pq=1/0 qp=1 dt=68850/0/0 df=31 of=8 ql=0/0 qs=.... kt=0/W ktl=14bd b=10 ci=77475 nci=0 co=508 ca=1042

  0!c=12865 g=12866 cnq=1/0:1 dt=83113/140000000000000/0 df=288 of=11 ql=0/0 qs=N... kt=0/O ktl=944 b=10 ci=60709 nci=0 co=748 ca=871

  1 c=14407 g=14408 cnq=1/0:0 dt=100679/140000000000000/0 df=378 of=7 ql=0/119 qs=NRW. kt=0/W ktl=9b6 b=10 ci=109740 nci=0 co=589 ca=485

  2 c=14407 g=14408 cnq=1/0:0 dt=105486/0/0 df=90 of=9 ql=0/89 qs=NRW. kt=0/W ktl=c0c b=10 ci=83113 nci=0 co=533 ca=490

  3 c=14407 g=14408 cnq=1/0:0 dt=107138/0/0 df=142 of=8 ql=0/188 qs=NRW. kt=0/W ktl=b96 b=10 ci=121114 nci=0 co=426 ca=290

  4 c=14405 g=14406 cnq=1/0:1 dt=50238/0/0 df=706 of=7 ql=0/0 qs=.... kt=0/W ktl=812 b=10 ci=34929 nci=0 co=643 ca=114

  5!c=14168 g=14169 cnq=1/0:0 dt=45465/140000000000000/0 df=161 of=11 ql=0/0 qs=N... kt=0/O ktl=b4d b=10 ci=47712 nci=0 co=677 ca=722

  6 c=14404 g=14405 cnq=1/0:0 dt=59454/0/0 df=94 of=6 ql=0/0 qs=.... kt=0/W ktl=e57 b=10 ci=55597 nci=0 co=701 ca=811

  7 c=14407 g=14408 cnq=1/0:1 dt=68850/0/0 df=31 of=8 ql=0/0 qs=.... kt=0/W ktl=14bd b=10 ci=77475 nci=0 co=508 ca=1042



This is similar to the output discussed above, but contains the following

additional fields:

Documentation/RCU/whatisRCU.txt

+3 −3
Original line number Diff line number Diff line
@@ -364,7 +364,7 @@ uses of RCU may be found in listRCU.txt, arrayRCU.txt, and NMI-RCU.txt. 
	};

	DEFINE_SPINLOCK(foo_mutex);



	struct foo *gbl_foo;

	struct foo __rcu *gbl_foo;



	/*

	 * Create a new struct foo that is the same as the one currently
@@ -386,7 +386,7 @@ uses of RCU may be found in listRCU.txt, arrayRCU.txt, and NMI-RCU.txt. 


		new_fp = kmalloc(sizeof(*new_fp), GFP_KERNEL);

		spin_lock(&foo_mutex);

		old_fp = gbl_foo;

		old_fp = rcu_dereference_protected(gbl_foo, lockdep_is_held(&foo_mutex));

		*new_fp = *old_fp;

		new_fp->a = new_a;

		rcu_assign_pointer(gbl_foo, new_fp);
@@ -487,7 +487,7 @@ The foo_update_a() function might then be written as follows: 


		new_fp = kmalloc(sizeof(*new_fp), GFP_KERNEL);

		spin_lock(&foo_mutex);

		old_fp = gbl_foo;

		old_fp = rcu_dereference_protected(gbl_foo, lockdep_is_held(&foo_mutex));

		*new_fp = *old_fp;

		new_fp->a = new_a;

		rcu_assign_pointer(gbl_foo, new_fp);

Documentation/kernel-parameters.txt

+6 −3
Original line number Diff line number Diff line
@@ -3089,9 +3089,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 
			cache-to-cache transfer latencies.



	rcutree.rcu_fanout_leaf= [KNL]

			Increase the number of CPUs assigned to each

			leaf rcu_node structure.  Useful for very large

			systems.

			Change the number of CPUs assigned to each

			leaf rcu_node structure.  Useful for very

			large systems, which will choose the value 64,

			and for NUMA systems with large remote-access

			latencies, which will choose a value aligned

			with the appropriate hardware boundaries.



	rcutree.jiffies_till_sched_qs= [KNL]

			Set required age in jiffies for a

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