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 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
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@@ -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/whatisRCU.txt

+3 −3
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@@ -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/locking/locktorture.txt

+3 −0
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@@ -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 "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.



torture_runnable  Start locktorture at boot time in the case where the

Documentation/memory-barriers.txt

+11 −1
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@@ -1710,6 +1710,17 @@ There are some more advanced barrier functions: 
     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_rmb();
@@ -1789,7 +1800,6 @@ The Linux kernel has a number of locking constructs: 
 (*) mutexes

 (*) semaphores

 (*) R/W semaphores

 (*) RCU



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

for each construct.  These operations all imply certain barriers: