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Commit 39cd2dd3 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

Merge branches 'doc.2015.10.06a', 'percpu-rwsem.2015.10.06a' and 'torture.2015.10.06a' into HEAD 

doc.2015.10.06a:  Documentation updates.
percpu-rwsem.2015.10.06a:  Optimization of per-CPU reader-writer semaphores.
torture.2015.10.06a:  Torture-test updates.
parents d2856b04 ad2ad5d3 4bace734 a36a9961

Documentation/RCU/stallwarn.txt

+7 −0
Original line number Original line 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()

	behavior, you might need to replace some of the cond_resched()

	calls with calls to cond_resched_rcu_qs().

	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.

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

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

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

	This message will include information on when the kthread last

	This message will include information on when the kthread last

Documentation/RCU/torture.txt

+13 −26
Original line number Original line 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:

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





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

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



			along with expedited, synchronous, and polling

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

			variants.

			synchronize_rcu().



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

			synchronize_rcu_expedited().





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

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

			call_rcu_bh().

			call_rcu_bh(), along with expedited and synchronous



			variants.

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

			and synchronize_rcu_bh().





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

		"rcu_busted": This tests an intentionally incorrect version

			and synchronize_rcu_bh_expedited().

			of RCU in order to help test rcutorture itself.





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

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

			call_srcu().

			call_srcu(), along with expedited and



			synchronous variants.

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

			synchronize_srcu().



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

			synchronize_srcu_expedited().





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

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

			call_rcu_sched().

			call_rcu_sched(), along with expedited,



			synchronous, and polling variants.

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

			synchronize_sched().





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

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

			synchronize_sched_expedited().

			along with expedited and synchronous variants.





		Defaults to "rcu".

		Defaults to "rcu".

Documentation/RCU/whatisRCU.txt

+3 −3
Original line number Original line 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);

	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

	 * 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);

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

		spin_lock(&foo_mutex);

		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 = *old_fp;

		new_fp->a = new_a;

		new_fp->a = new_a;

		rcu_assign_pointer(gbl_foo, new_fp);

		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);

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

		spin_lock(&foo_mutex);

		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 = *old_fp;

		new_fp->a = new_a;

		new_fp->a = new_a;

		rcu_assign_pointer(gbl_foo, new_fp);

		rcu_assign_pointer(gbl_foo, new_fp);

Documentation/locking/locktorture.txt

+3 −0
Original line number Original line Diff line number Diff line
@@ -52,6 +52,9 @@ torture_type Type of lock to torture. By default, only spinlocks will 




		     o "mutex_lock": mutex_lock() and mutex_unlock() pairs.

		     o "mutex_lock": mutex_lock() and mutex_unlock() pairs.





		     o "rtmutex_lock": rtmutex_lock() and rtmutex_unlock()

				       pairs. Kernel must have CONFIG_RT_MUTEX=y.



		     o "rwsem_lock": read/write down() and up() semaphore pairs.

		     o "rwsem_lock": read/write down() and up() semaphore pairs.





torture_runnable  Start locktorture at boot time in the case where the

torture_runnable  Start locktorture at boot time in the case where the

Documentation/memory-barriers.txt

+11 −1
Original line number Original line Diff line number Diff line
@@ -1710,6 +1710,17 @@ There are some more advanced barrier functions: 
     operations" subsection for information on where to use these.

     operations" subsection for information on where to use these.









 (*) lockless_dereference();

     This can be thought of as a pointer-fetch wrapper around the

     smp_read_barrier_depends() data-dependency barrier.



     This is also similar to rcu_dereference(), but in cases where

     object lifetime is handled by some mechanism other than RCU, for

     example, when the objects removed only when the system goes down.

     In addition, lockless_dereference() is used in some data structures

     that can be used both with and without RCU.





 (*) dma_wmb();

 (*) dma_wmb();

 (*) dma_rmb();

 (*) dma_rmb();
@@ -1789,7 +1800,6 @@ The Linux kernel has a number of locking constructs: 
 (*) mutexes

 (*) mutexes

 (*) semaphores

 (*) semaphores

 (*) R/W semaphores

 (*) R/W semaphores

 (*) RCU





In all cases there are variants on "ACQUIRE" operations and "RELEASE" operations

In all cases there are variants on "ACQUIRE" operations and "RELEASE" operations

for each construct.  These operations all imply certain barriers:

for each construct.  These operations all imply certain barriers: