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Commit e84cf5d0 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:
 "SRCU changes:

   - These include debugging aids, updates that move towards the goal of
     permitting srcu_read_lock() and srcu_read_unlock() to be used from
     idle and offline CPUs, and a few small fixes.

  Changes to rcutorture and to RCU documentation:

   - Posted to LKML at https://lkml.org/lkml/2013/1/26/188

  Enhancements to uniprocessor handling in tiny RCU:

   - Posted to LKML at https://lkml.org/lkml/2013/1/27/2

  Tag RCU callbacks with grace-period number to simplify callback
  advancement:

   - Posted to LKML at https://lkml.org/lkml/2013/1/26/203

  Miscellaneous fixes:

   - Posted to LKML at https://lkml.org/lkml/2013/1/26/204"

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (27 commits)
  srcu: use ACCESS_ONCE() to access sp->completed in srcu_read_lock()
  srcu: Update synchronize_srcu_expedited()'s comments
  srcu: Update synchronize_srcu()'s comments
  srcu: Remove checks preventing idle CPUs from calling srcu_read_lock()
  srcu: Remove checks preventing offline CPUs from calling srcu_read_lock()
  srcu: Simple cleanup for cleanup_srcu_struct()
  srcu: Add might_sleep() annotation to synchronize_srcu()
  srcu: Simplify __srcu_read_unlock() via this_cpu_dec()
  rcu: Allow rcutorture to be built at low optimization levels
  rcu: Make rcutorture's shuffler task shuffle recently added tasks
  rcu: Allow TREE_PREEMPT_RCU on UP systems
  rcu: Provide RCU CPU stall warnings for tiny RCU
  context_tracking: Add comments on interface and internals
  rcu: Remove obsolete Kconfig option from comment
  rcu: Remove unused code originally used for context tracking
  rcu: Consolidate debugging Kconfig options
  rcu: Correct 'optimized' to 'optimize' in header comment
  rcu: Trace callback acceleration
  rcu: Tag callback lists with corresponding grace-period number
  rcutorture: Don't compare ptr with 0
  ...
parents 19f949f5 ac0e3202

Documentation/atomic_ops.txt

+2 −0
Original line number Diff line number Diff line
@@ -253,6 +253,8 @@ This performs an atomic exchange operation on the atomic variable v, setting 
the given new value.  It returns the old value that the atomic variable v had

just before the operation.



atomic_xchg requires explicit memory barriers around the operation.



	int atomic_cmpxchg(atomic_t *v, int old, int new);



This performs an atomic compare exchange operation on the atomic value v,

Documentation/memory-barriers.txt

+1 −0
Original line number Diff line number Diff line
@@ -1685,6 +1685,7 @@ explicit lock operations, described later). These include: 


	xchg();

	cmpxchg();

	atomic_xchg();

	atomic_cmpxchg();

	atomic_inc_return();

	atomic_dec_return();

include/linux/rcupdate.h

+11 −4
Original line number Diff line number Diff line
@@ -53,7 +53,10 @@ extern int rcutorture_runnable; /* for sysctl */ 
extern void rcutorture_record_test_transition(void);

extern void rcutorture_record_progress(unsigned long vernum);

extern void do_trace_rcu_torture_read(char *rcutorturename,

				      struct rcu_head *rhp);

				      struct rcu_head *rhp,

				      unsigned long secs,

				      unsigned long c_old,

				      unsigned long c);

#else

static inline void rcutorture_record_test_transition(void)

{
@@ -63,9 +66,13 @@ static inline void rcutorture_record_progress(unsigned long vernum) 
}

#ifdef CONFIG_RCU_TRACE

extern void do_trace_rcu_torture_read(char *rcutorturename,

				      struct rcu_head *rhp);

				      struct rcu_head *rhp,

				      unsigned long secs,

				      unsigned long c_old,

				      unsigned long c);

#else

#define do_trace_rcu_torture_read(rcutorturename, rhp) do { } while (0)

#define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \

	do { } while (0)

#endif

#endif
@@ -749,7 +756,7 @@ static inline void rcu_preempt_sleep_check(void) 
 * preemptible RCU implementations (TREE_PREEMPT_RCU and TINY_PREEMPT_RCU)

 * in CONFIG_PREEMPT kernel builds, RCU read-side critical sections may

 * be preempted, but explicit blocking is illegal.  Finally, in preemptible

 * RCU implementations in real-time (CONFIG_PREEMPT_RT) kernel builds,

 * RCU implementations in real-time (with -rt patchset) kernel builds,

 * RCU read-side critical sections may be preempted and they may also

 * block, but only when acquiring spinlocks that are subject to priority

 * inheritance.

include/linux/srcu.h

+3 −23
Original line number Diff line number Diff line
@@ -151,30 +151,14 @@ void srcu_barrier(struct srcu_struct *sp); 
 * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot

 * and while lockdep is disabled.

 *

 * Note that if the CPU is in the idle loop from an RCU point of view

 * (ie: that we are in the section between rcu_idle_enter() and

 * rcu_idle_exit()) then srcu_read_lock_held() returns false even if

 * the CPU did an srcu_read_lock().  The reason for this is that RCU

 * ignores CPUs that are in such a section, considering these as in

 * extended quiescent state, so such a CPU is effectively never in an

 * RCU read-side critical section regardless of what RCU primitives it

 * invokes.  This state of affairs is required --- we need to keep an

 * RCU-free window in idle where the CPU may possibly enter into low

 * power mode. This way we can notice an extended quiescent state to

 * other CPUs that started a grace period. Otherwise we would delay any

 * grace period as long as we run in the idle task.

 *

 * Similarly, we avoid claiming an SRCU read lock held if the current

 * CPU is offline.

 * Note that SRCU is based on its own statemachine and it doesn't

 * relies on normal RCU, it can be called from the CPU which

 * is in the idle loop from an RCU point of view or offline.

 */

static inline int srcu_read_lock_held(struct srcu_struct *sp)

{

	if (!debug_lockdep_rcu_enabled())

		return 1;

	if (rcu_is_cpu_idle())

		return 0;

	if (!rcu_lockdep_current_cpu_online())

		return 0;

	return lock_is_held(&sp->dep_map);

}
@@ -236,8 +220,6 @@ static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp) 
	int retval = __srcu_read_lock(sp);



	rcu_lock_acquire(&(sp)->dep_map);

	rcu_lockdep_assert(!rcu_is_cpu_idle(),

			   "srcu_read_lock() used illegally while idle");

	return retval;

}
@@ -251,8 +233,6 @@ static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp) 
static inline void srcu_read_unlock(struct srcu_struct *sp, int idx)

	__releases(sp)

{

	rcu_lockdep_assert(!rcu_is_cpu_idle(),

			   "srcu_read_unlock() used illegally while idle");

	rcu_lock_release(&(sp)->dep_map);

	__srcu_read_unlock(sp, idx);

}

include/trace/events/rcu.h

+21 −10
Original line number Diff line number Diff line
@@ -44,8 +44,10 @@ TRACE_EVENT(rcu_utilization, 
 * of a new grace period or the end of an old grace period ("cpustart"

 * and "cpuend", respectively), a CPU passing through a quiescent

 * state ("cpuqs"), a CPU coming online or going offline ("cpuonl"

 * and "cpuofl", respectively), and a CPU being kicked for being too

 * long in dyntick-idle mode ("kick").

 * and "cpuofl", respectively), a CPU being kicked for being too

 * long in dyntick-idle mode ("kick"), a CPU accelerating its new

 * callbacks to RCU_NEXT_READY_TAIL ("AccReadyCB"), and a CPU

 * accelerating its new callbacks to RCU_WAIT_TAIL ("AccWaitCB").

 */

TRACE_EVENT(rcu_grace_period,
@@ -393,7 +395,7 @@ TRACE_EVENT(rcu_kfree_callback, 
 */

TRACE_EVENT(rcu_batch_start,



	TP_PROTO(char *rcuname, long qlen_lazy, long qlen, int blimit),

	TP_PROTO(char *rcuname, long qlen_lazy, long qlen, long blimit),



	TP_ARGS(rcuname, qlen_lazy, qlen, blimit),
@@ -401,7 +403,7 @@ TRACE_EVENT(rcu_batch_start, 
		__field(char *, rcuname)

		__field(long, qlen_lazy)

		__field(long, qlen)

		__field(int, blimit)

		__field(long, blimit)

	),



	TP_fast_assign(
@@ -411,7 +413,7 @@ TRACE_EVENT(rcu_batch_start, 
		__entry->blimit = blimit;

	),



	TP_printk("%s CBs=%ld/%ld bl=%d",

	TP_printk("%s CBs=%ld/%ld bl=%ld",

		  __entry->rcuname, __entry->qlen_lazy, __entry->qlen,

		  __entry->blimit)

);
@@ -523,22 +525,30 @@ TRACE_EVENT(rcu_batch_end, 
 */

TRACE_EVENT(rcu_torture_read,



	TP_PROTO(char *rcutorturename, struct rcu_head *rhp),

	TP_PROTO(char *rcutorturename, struct rcu_head *rhp,

		 unsigned long secs, unsigned long c_old, unsigned long c),



	TP_ARGS(rcutorturename, rhp),

	TP_ARGS(rcutorturename, rhp, secs, c_old, c),



	TP_STRUCT__entry(

		__field(char *, rcutorturename)

		__field(struct rcu_head *, rhp)

		__field(unsigned long, secs)

		__field(unsigned long, c_old)

		__field(unsigned long, c)

	),



	TP_fast_assign(

		__entry->rcutorturename = rcutorturename;

		__entry->rhp = rhp;

		__entry->secs = secs;

		__entry->c_old = c_old;

		__entry->c = c;

	),



	TP_printk("%s torture read %p",

		  __entry->rcutorturename, __entry->rhp)

	TP_printk("%s torture read %p %luus c: %lu %lu",

		  __entry->rcutorturename, __entry->rhp,

		  __entry->secs, __entry->c_old, __entry->c)

);



/*
@@ -608,7 +618,8 @@ TRACE_EVENT(rcu_barrier, 
#define trace_rcu_invoke_kfree_callback(rcuname, rhp, offset) do { } while (0)

#define trace_rcu_batch_end(rcuname, callbacks_invoked, cb, nr, iit, risk) \

	do { } while (0)

#define trace_rcu_torture_read(rcutorturename, rhp) do { } while (0)

#define trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \

	do { } while (0)

#define trace_rcu_barrier(name, s, cpu, cnt, done) do { } while (0)



#endif /* #else #ifdef CONFIG_RCU_TRACE */