Commit 8747a291 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 updates from Ingo Molnar:
 "The main RCU subsystem changes in this cycle were:

  - Miscellaneous fixes, perhaps most notably removing obsolete code
    whose only purpose in life was to gather information for the
    now-removed RCU debugfs facility. Other notable changes include
    removing NO_HZ_FULL_ALL in favor of the nohz_full kernel boot
    parameter, minor optimizations for expedited grace periods, some
    added tracing, creating an RCU-specific workqueue using Tejun's new
    WQ_MEM_RECLAIM flag, and several cleanups to code and comments.

  - SRCU cleanups and optimizations.

  - Torture-test updates, perhaps most notably the adding of ARMv8
    support, but also including numerous cleanups and usability fixes"

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (37 commits)
  rcu: Create RCU-specific workqueues with rescuers
  torture: Provide more sensible nreader/nwriter defaults for rcuperf
  torture: Grace periods do not piggyback off of themselves
  torture: Adjust rcuperf trace processing to allow for workqueues
  torture: Default jitter off when running rcuperf
  torture: Specify qemu memory size with --memory argument
  rcutorture: Add basic ARM64 support to run scripts
  rcutorture: Update kvm.sh header comment
  rcutorture: Record which grace-period primitives are tested
  rcutorture: Re-enable testing of dynamic expediting
  rcutorture: Avoid fake-writer use of undefined primitives
  rcutorture: Abstract function and module names
  rcutorture: Replace multi-instance kzalloc() with kcalloc()
  rcu: Remove SRCU throttling
  srcu: Remove dead code in srcu_gp_end()
  srcu: Reduce scans of srcu_data in counter wrap check
  srcu: Prevent sdp->srcu_gp_seq_needed_exp counter wrap
  srcu: Abstract function name
  rcu: Make expedited RCU CPU selection avoid unnecessary stores
  rcu: Trace expedited GP delays due to transitioning CPUs
  ...
parents cc67ccec c4fb5f37

Documentation/timers/NO_HZ.txt

+0 −7
Original line number Diff line number Diff line
@@ -131,13 +131,6 @@ error message, and the boot CPU will be removed from the mask. Note that 
this means that your system must have at least two CPUs in order for

CONFIG_NO_HZ_FULL=y to do anything for you.



Alternatively, the CONFIG_NO_HZ_FULL_ALL=y Kconfig parameter specifies

that all CPUs other than the boot CPU are adaptive-ticks CPUs.  This

Kconfig parameter will be overridden by the "nohz_full=" boot parameter,

so that if both the CONFIG_NO_HZ_FULL_ALL=y Kconfig parameter and

the "nohz_full=1" boot parameter is specified, the boot parameter will

prevail so that only CPU 1 will be an adaptive-ticks CPU.



Finally, adaptive-ticks CPUs must have their RCU callbacks offloaded.

This is covered in the "RCU IMPLICATIONS" section below.

include/linux/rcupdate.h

+6 −4
Original line number Diff line number Diff line
@@ -214,10 +214,12 @@ do { \ 
#endif



/*

 * init_rcu_head_on_stack()/destroy_rcu_head_on_stack() are needed for dynamic

 * initialization and destruction of rcu_head on the stack. rcu_head structures

 * allocated dynamically in the heap or defined statically don't need any

 * initialization.

 * The init_rcu_head_on_stack() and destroy_rcu_head_on_stack() calls

 * are needed for dynamic initialization and destruction of rcu_head

 * on the stack, and init_rcu_head()/destroy_rcu_head() are needed for

 * dynamic initialization and destruction of statically allocated rcu_head

 * structures.  However, rcu_head structures allocated dynamically in the

 * heap don't need any initialization.

 */

#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD

void init_rcu_head(struct rcu_head *head);

include/linux/types.h

+1 −1
Original line number Diff line number Diff line
@@ -217,7 +217,7 @@ struct ustat { 
 *

 * This guarantee is important for few reasons:

 *  - future call_rcu_lazy() will make use of lower bits in the pointer;

 *  - the structure shares storage spacer in struct page with @compound_head,

 *  - the structure shares storage space in struct page with @compound_head,

 *    which encode PageTail() in bit 0. The guarantee is needed to avoid

 *    false-positive PageTail().

 */

include/trace/events/rcu.h

+4 −0
Original line number Diff line number Diff line
@@ -179,6 +179,10 @@ TRACE_EVENT(rcu_grace_period_init, 
 *

 *	"snap": Captured snapshot of expedited grace period sequence number.

 *	"start": Started a real expedited grace period.

 *	"reset": Started resetting the tree

 *	"select": Started selecting the CPUs to wait on.

 *	"selectofl": Selected CPU partially offline.

 *	"startwait": Started waiting on selected CPUs.

 *	"end": Ended a real expedited grace period.

 *	"endwake": Woke piggybackers up.

 *	"done": Someone else did the expedited grace period for us.

kernel/rcu/rcu.h

+27 −11
Original line number Diff line number Diff line
@@ -77,12 +77,18 @@ static inline void rcu_seq_start(unsigned long *sp) 
	WARN_ON_ONCE(rcu_seq_state(*sp) != 1);

}



/* Compute the end-of-grace-period value for the specified sequence number. */

static inline unsigned long rcu_seq_endval(unsigned long *sp)

{

	return (*sp | RCU_SEQ_STATE_MASK) + 1;

}



/* Adjust sequence number for end of update-side operation. */

static inline void rcu_seq_end(unsigned long *sp)

{

	smp_mb(); /* Ensure update-side operation before counter increment. */

	WARN_ON_ONCE(!rcu_seq_state(*sp));

	WRITE_ONCE(*sp, (*sp | RCU_SEQ_STATE_MASK) + 1);

	WRITE_ONCE(*sp, rcu_seq_endval(sp));

}



/* Take a snapshot of the update side's sequence number. */
@@ -295,9 +301,19 @@ static inline void rcu_init_levelspread(int *levelspread, const int *levelcnt) 
 * Iterate over all possible CPUs in a leaf RCU node.

 */

#define for_each_leaf_node_possible_cpu(rnp, cpu) \

	for ((cpu) = cpumask_next(rnp->grplo - 1, cpu_possible_mask); \

	     cpu <= rnp->grphi; \

	     cpu = cpumask_next((cpu), cpu_possible_mask))

	for ((cpu) = cpumask_next((rnp)->grplo - 1, cpu_possible_mask); \

	     (cpu) <= rnp->grphi; \

	     (cpu) = cpumask_next((cpu), cpu_possible_mask))



/*

 * Iterate over all CPUs in a leaf RCU node's specified mask.

 */

#define rcu_find_next_bit(rnp, cpu, mask) \

	((rnp)->grplo + find_next_bit(&(mask), BITS_PER_LONG, (cpu)))

#define for_each_leaf_node_cpu_mask(rnp, cpu, mask) \

	for ((cpu) = rcu_find_next_bit((rnp), 0, (mask)); \

	     (cpu) <= rnp->grphi; \

	     (cpu) = rcu_find_next_bit((rnp), (cpu) + 1 - (rnp->grplo), (mask)))



/*

 * Wrappers for the rcu_node::lock acquire and release.
@@ -337,7 +353,7 @@ do { \ 
} while (0)



#define raw_spin_unlock_irqrestore_rcu_node(p, flags)			\

	raw_spin_unlock_irqrestore(&ACCESS_PRIVATE(p, lock), flags)	\

	raw_spin_unlock_irqrestore(&ACCESS_PRIVATE(p, lock), flags)



#define raw_spin_trylock_rcu_node(p)					\

({									\
@@ -348,6 +364,9 @@ do { \ 
	___locked;							\

})



#define raw_lockdep_assert_held_rcu_node(p)				\

	lockdep_assert_held(&ACCESS_PRIVATE(p, lock))



#endif /* #if defined(SRCU) || !defined(TINY_RCU) */



#ifdef CONFIG_TINY_RCU
@@ -356,24 +375,20 @@ static inline bool rcu_gp_is_normal(void) { return true; } 
static inline bool rcu_gp_is_expedited(void) { return false; }

static inline void rcu_expedite_gp(void) { }

static inline void rcu_unexpedite_gp(void) { }

static inline void rcu_request_urgent_qs_task(struct task_struct *t) { }

#else /* #ifdef CONFIG_TINY_RCU */

bool rcu_gp_is_normal(void);     /* Internal RCU use. */

bool rcu_gp_is_expedited(void);  /* Internal RCU use. */

void rcu_expedite_gp(void);

void rcu_unexpedite_gp(void);

void rcupdate_announce_bootup_oddness(void);

void rcu_request_urgent_qs_task(struct task_struct *t);

#endif /* #else #ifdef CONFIG_TINY_RCU */



#define RCU_SCHEDULER_INACTIVE	0

#define RCU_SCHEDULER_INIT	1

#define RCU_SCHEDULER_RUNNING	2



#ifdef CONFIG_TINY_RCU

static inline void rcu_request_urgent_qs_task(struct task_struct *t) { }

#else /* #ifdef CONFIG_TINY_RCU */

void rcu_request_urgent_qs_task(struct task_struct *t);

#endif /* #else #ifdef CONFIG_TINY_RCU */



enum rcutorture_type {

	RCU_FLAVOR,

	RCU_BH_FLAVOR,
@@ -470,6 +485,7 @@ void show_rcu_gp_kthreads(void); 
void rcu_force_quiescent_state(void);

void rcu_bh_force_quiescent_state(void);

void rcu_sched_force_quiescent_state(void);

extern struct workqueue_struct *rcu_gp_wq;

#endif /* #else #ifdef CONFIG_TINY_RCU */



#ifdef CONFIG_RCU_NOCB_CPU

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