Merge branch 'for-mingo' of... (567b64aa) · Commits · e / devices / android_kernel_oneplus_sm8150

Documentation/RCU/00-INDEX

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Original line number	Original line	Diff line number	Diff line
	@@ -28,8 +28,6 @@ stallwarn.txt
	- RCU CPU stall warnings (module parameter rcu_cpu_stall_suppress)		- RCU CPU stall warnings (module parameter rcu_cpu_stall_suppress)
	torture.txt		torture.txt
	- RCU Torture Test Operation (CONFIG_RCU_TORTURE_TEST)		- RCU Torture Test Operation (CONFIG_RCU_TORTURE_TEST)
	trace.txt
	- CONFIG_RCU_TRACE debugfs files and formats
	UP.txt		UP.txt
	- RCU on Uniprocessor Systems		- RCU on Uniprocessor Systems
	whatisRCU.txt		whatisRCU.txt

Documentation/RCU/Design/Requirements/Requirements.html

+21 −13

Original line number	Original line	Diff line number	Diff line
	@@ -559,9 +559,7 @@ The <tt>rcu_access_pointer()</tt> on line 6 is similar to
	For <tt>remove_gp_synchronous()</tt>, as long as all modifications		For <tt>remove_gp_synchronous()</tt>, as long as all modifications
	to <tt>gp</tt> are carried out while holding <tt>gp_lock</tt>,		to <tt>gp</tt> are carried out while holding <tt>gp_lock</tt>,
	the above optimizations are harmless.		the above optimizations are harmless.
	However,		However, <tt>sparse</tt> will complain if you
	with <tt>CONFIG_SPARSE_RCU_POINTER=y</tt>,
	<tt>sparse</tt> will complain if you
	define <tt>gp</tt> with <tt>__rcu</tt> and then		define <tt>gp</tt> with <tt>__rcu</tt> and then
	access it without using		access it without using
	either <tt>rcu_access_pointer()</tt> or <tt>rcu_dereference()</tt>.		either <tt>rcu_access_pointer()</tt> or <tt>rcu_dereference()</tt>.
	@@ -1849,7 +1847,8 @@ mass storage, or user patience, whichever comes first.
	If the nesting is not visible to the compiler, as is the case with		If the nesting is not visible to the compiler, as is the case with
	mutually recursive functions each in its own translation unit,		mutually recursive functions each in its own translation unit,
	stack overflow will result.		stack overflow will result.
	If the nesting takes the form of loops, either the control variable		If the nesting takes the form of loops, perhaps in the guise of tail
			recursion, either the control variable
	will overflow or (in the Linux kernel) you will get an RCU CPU stall warning.		will overflow or (in the Linux kernel) you will get an RCU CPU stall warning.
	Nevertheless, this class of RCU implementations is one		Nevertheless, this class of RCU implementations is one
	of the most composable constructs in existence.		of the most composable constructs in existence.
	@@ -1977,9 +1976,8 @@ guard against mishaps and misuse:
	and <tt>rcu_dereference()</tt>, perhaps (incorrectly)		and <tt>rcu_dereference()</tt>, perhaps (incorrectly)
	substituting a simple assignment.		substituting a simple assignment.
	To catch this sort of error, a given RCU-protected pointer may be		To catch this sort of error, a given RCU-protected pointer may be
	tagged with <tt>__rcu</tt>, after which running sparse		tagged with <tt>__rcu</tt>, after which sparse
	with <tt>CONFIG_SPARSE_RCU_POINTER=y</tt> will complain		will complain about simple-assignment accesses to that pointer.
	about simple-assignment accesses to that pointer.
	Arnd Bergmann made me aware of this requirement, and also		Arnd Bergmann made me aware of this requirement, and also
	supplied the needed		supplied the needed
	<a href="https://lwn.net/Articles/376011/">patch series</a>.		<a href="https://lwn.net/Articles/376011/">patch series</a>.
	@@ -2036,7 +2034,7 @@ guard against mishaps and misuse:
	some other synchronization mechanism, for example, reference		some other synchronization mechanism, for example, reference
	counting.		counting.
	<li> In kernels built with <tt>CONFIG_RCU_TRACE=y</tt>, RCU-related		<li> In kernels built with <tt>CONFIG_RCU_TRACE=y</tt>, RCU-related
	information is provided via both debugfs and event tracing.		information is provided via event tracing.
	<li> Open-coded use of <tt>rcu_assign_pointer()</tt> and		<li> Open-coded use of <tt>rcu_assign_pointer()</tt> and
	<tt>rcu_dereference()</tt> to create typical linked		<tt>rcu_dereference()</tt> to create typical linked
	data structures can be surprisingly error-prone.		data structures can be surprisingly error-prone.
	@@ -2519,11 +2517,7 @@ It is similarly socially unacceptable to interrupt an
	<tt>nohz_full</tt> CPU running in userspace.		<tt>nohz_full</tt> CPU running in userspace.
	RCU must therefore track <tt>nohz_full</tt> userspace		RCU must therefore track <tt>nohz_full</tt> userspace
	execution.		execution.
	And in		RCU must therefore be able to sample state at two points in
	<a href="https://lwn.net/Articles/558284/"><tt>CONFIG_NO_HZ_FULL_SYSIDLE=y</tt></a>
	kernels, RCU must separately track idle CPUs on the one hand and
	CPUs that are either idle or executing in userspace on the other.
	In both cases, RCU must be able to sample state at two points in
	time, and be able to determine whether or not some other CPU spent		time, and be able to determine whether or not some other CPU spent
	any time idle and/or executing in userspace.		any time idle and/or executing in userspace.

	@@ -2935,6 +2929,20 @@ The reason that this is possible is that SRCU is insensitive
	to whether or not a CPU is online, which means that <tt>srcu_barrier()</tt>		to whether or not a CPU is online, which means that <tt>srcu_barrier()</tt>
	need not exclude CPU-hotplug operations.		need not exclude CPU-hotplug operations.

			<p>
			SRCU also differs from other RCU flavors in that SRCU's expedited and
			non-expedited grace periods are implemented by the same mechanism.
			This means that in the current SRCU implementation, expediting a
			future grace period has the side effect of expediting all prior
			grace periods that have not yet completed.
			(But please note that this is a property of the current implementation,
			not necessarily of future implementations.)
			In addition, if SRCU has been idle for longer than the interval
			specified by the <tt>srcutree.exp_holdoff</tt> kernel boot parameter
			(25 microseconds by default),
			and if a <tt>synchronize_srcu()</tt> invocation ends this idle period,
			that invocation will be automatically expedited.

	<p>		<p>
	As of v4.12, SRCU's callbacks are maintained per-CPU, eliminating		As of v4.12, SRCU's callbacks are maintained per-CPU, eliminating
	a locking bottleneck present in prior kernel versions.		a locking bottleneck present in prior kernel versions.

Documentation/RCU/checklist.txt

+4 −4

Original line number	Original line	Diff line number	Diff line
	@@ -413,11 +413,11 @@ over a rather long period of time, but improvements are always welcome!
	read-side critical sections. It is the responsibility of the		read-side critical sections. It is the responsibility of the
	RCU update-side primitives to deal with this.		RCU update-side primitives to deal with this.

	17. Use CONFIG_PROVE_RCU, CONFIG_DEBUG_OBJECTS_RCU_HEAD, and the		17. Use CONFIG_PROVE_LOCKING, CONFIG_DEBUG_OBJECTS_RCU_HEAD, and the
	__rcu sparse checks (enabled by CONFIG_SPARSE_RCU_POINTER) to		__rcu sparse checks to validate your RCU code. These can help
	validate your RCU code. These can help find problems as follows:		find problems as follows:

	CONFIG_PROVE_RCU: check that accesses to RCU-protected data		CONFIG_PROVE_LOCKING: check that accesses to RCU-protected data
	structures are carried out under the proper RCU		structures are carried out under the proper RCU
	read-side critical section, while holding the right		read-side critical section, while holding the right
	combination of locks, or whatever other conditions		combination of locks, or whatever other conditions

Documentation/RCU/trace.txt

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Documentation/admin-guide/kernel-parameters.txt

+31 −10

Original line number	Original line	Diff line number	Diff line
	@@ -3238,21 +3238,17 @@

	rcutree.gp_cleanup_delay= [KNL]		rcutree.gp_cleanup_delay= [KNL]
	Set the number of jiffies to delay each step of		Set the number of jiffies to delay each step of
	RCU grace-period cleanup. This only has effect		RCU grace-period cleanup.
	when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.

	rcutree.gp_init_delay= [KNL]		rcutree.gp_init_delay= [KNL]
	Set the number of jiffies to delay each step of		Set the number of jiffies to delay each step of
	RCU grace-period initialization. This only has		RCU grace-period initialization.
	effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
	is set.

	rcutree.gp_preinit_delay= [KNL]		rcutree.gp_preinit_delay= [KNL]
	Set the number of jiffies to delay each step of		Set the number of jiffies to delay each step of
	RCU grace-period pre-initialization, that is,		RCU grace-period pre-initialization, that is,
	the propagation of recent CPU-hotplug changes up		the propagation of recent CPU-hotplug changes up
	the rcu_node combining tree. This only has effect		the rcu_node combining tree.
	when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.

	rcutree.rcu_fanout_exact= [KNL]		rcutree.rcu_fanout_exact= [KNL]
	Disable autobalancing of the rcu_node combining		Disable autobalancing of the rcu_node combining
	@@ -3328,6 +3324,17 @@
	This wake_up() will be accompanied by a		This wake_up() will be accompanied by a
	WARN_ONCE() splat and an ftrace_dump().		WARN_ONCE() splat and an ftrace_dump().

			rcuperf.gp_async= [KNL]
			Measure performance of asynchronous
			grace-period primitives such as call_rcu().

			rcuperf.gp_async_max= [KNL]
			Specify the maximum number of outstanding
			callbacks per writer thread. When a writer
			thread exceeds this limit, it invokes the
			corresponding flavor of rcu_barrier() to allow
			previously posted callbacks to drain.

	rcuperf.gp_exp= [KNL]		rcuperf.gp_exp= [KNL]
	Measure performance of expedited synchronous		Measure performance of expedited synchronous
	grace-period primitives.		grace-period primitives.
	@@ -3355,17 +3362,22 @@
	rcuperf.perf_runnable= [BOOT]		rcuperf.perf_runnable= [BOOT]
	Start rcuperf running at boot time.		Start rcuperf running at boot time.

			rcuperf.perf_type= [KNL]
			Specify the RCU implementation to test.

	rcuperf.shutdown= [KNL]		rcuperf.shutdown= [KNL]
	Shut the system down after performance tests		Shut the system down after performance tests
	complete. This is useful for hands-off automated		complete. This is useful for hands-off automated
	testing.		testing.

	rcuperf.perf_type= [KNL]
	Specify the RCU implementation to test.

	rcuperf.verbose= [KNL]		rcuperf.verbose= [KNL]
	Enable additional printk() statements.		Enable additional printk() statements.

			rcuperf.writer_holdoff= [KNL]
			Write-side holdoff between grace periods,
			in microseconds. The default of zero says
			no holdoff.

	rcutorture.cbflood_inter_holdoff= [KNL]		rcutorture.cbflood_inter_holdoff= [KNL]
	Set holdoff time (jiffies) between successive		Set holdoff time (jiffies) between successive
	callback-flood tests.		callback-flood tests.
	@@ -3803,6 +3815,15 @@
	spia_pedr=		spia_pedr=
	spia_peddr=		spia_peddr=

			srcutree.counter_wrap_check [KNL]
			Specifies how frequently to check for
			grace-period sequence counter wrap for the
			srcu_data structure's ->srcu_gp_seq_needed field.
			The greater the number of bits set in this kernel
			parameter, the less frequently counter wrap will
			be checked for. Note that the bottom two bits
			are ignored.

	srcutree.exp_holdoff [KNL]		srcutree.exp_holdoff [KNL]
	Specifies how many nanoseconds must elapse		Specifies how many nanoseconds must elapse
	since the end of the last SRCU grace period for		since the end of the last SRCU grace period for