mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-25 13:43:55 +08:00
3d76c08290
Whitespace fixes, updated comments, and trivial code movement. o Fix whitespace error in RCU_HEAD_INIT() o Move "So where is rcu_write_lock()" comment so that it does not come between the rcu_read_unlock() header comment and the rcu_read_unlock() definition. o Move the module_param statements for blimit, qhimark, and qlowmark to immediately follow the corresponding definitions. o In __rcu_offline_cpu(), move the assignment to rdp_me inside the "if" statement, given that rdp_me is not used outside of that "if" statement. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: akpm@linux-foundation.org Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com LKML-Reference: <12541491931164-git-send-email-> Signed-off-by: Ingo Molnar <mingo@elte.hu>
309 lines
10 KiB
C
309 lines
10 KiB
C
/*
|
|
* Read-Copy Update mechanism for mutual exclusion
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License as published by
|
|
* the Free Software Foundation; either version 2 of the License, or
|
|
* (at your option) any later version.
|
|
*
|
|
* This program is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
* GNU General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU General Public License
|
|
* along with this program; if not, write to the Free Software
|
|
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
|
|
*
|
|
* Copyright IBM Corporation, 2001
|
|
*
|
|
* Author: Dipankar Sarma <dipankar@in.ibm.com>
|
|
*
|
|
* Based on the original work by Paul McKenney <paulmck@us.ibm.com>
|
|
* and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
|
|
* Papers:
|
|
* http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
|
|
* http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
|
|
*
|
|
* For detailed explanation of Read-Copy Update mechanism see -
|
|
* http://lse.sourceforge.net/locking/rcupdate.html
|
|
*
|
|
*/
|
|
|
|
#ifndef __LINUX_RCUPDATE_H
|
|
#define __LINUX_RCUPDATE_H
|
|
|
|
#include <linux/cache.h>
|
|
#include <linux/spinlock.h>
|
|
#include <linux/threads.h>
|
|
#include <linux/cpumask.h>
|
|
#include <linux/seqlock.h>
|
|
#include <linux/lockdep.h>
|
|
#include <linux/completion.h>
|
|
|
|
/**
|
|
* struct rcu_head - callback structure for use with RCU
|
|
* @next: next update requests in a list
|
|
* @func: actual update function to call after the grace period.
|
|
*/
|
|
struct rcu_head {
|
|
struct rcu_head *next;
|
|
void (*func)(struct rcu_head *head);
|
|
};
|
|
|
|
/* Exported common interfaces */
|
|
#ifdef CONFIG_TREE_PREEMPT_RCU
|
|
extern void synchronize_rcu(void);
|
|
#else /* #ifdef CONFIG_TREE_PREEMPT_RCU */
|
|
#define synchronize_rcu synchronize_sched
|
|
#endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */
|
|
extern void synchronize_rcu_bh(void);
|
|
extern void synchronize_sched(void);
|
|
extern void rcu_barrier(void);
|
|
extern void rcu_barrier_bh(void);
|
|
extern void rcu_barrier_sched(void);
|
|
extern void synchronize_sched_expedited(void);
|
|
extern int sched_expedited_torture_stats(char *page);
|
|
|
|
/* Internal to kernel */
|
|
extern void rcu_init(void);
|
|
extern void rcu_scheduler_starting(void);
|
|
extern int rcu_needs_cpu(int cpu);
|
|
extern int rcu_scheduler_active;
|
|
|
|
#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU)
|
|
#include <linux/rcutree.h>
|
|
#else
|
|
#error "Unknown RCU implementation specified to kernel configuration"
|
|
#endif
|
|
|
|
#define RCU_HEAD_INIT { .next = NULL, .func = NULL }
|
|
#define RCU_HEAD(head) struct rcu_head head = RCU_HEAD_INIT
|
|
#define INIT_RCU_HEAD(ptr) do { \
|
|
(ptr)->next = NULL; (ptr)->func = NULL; \
|
|
} while (0)
|
|
|
|
#ifdef CONFIG_DEBUG_LOCK_ALLOC
|
|
extern struct lockdep_map rcu_lock_map;
|
|
# define rcu_read_acquire() \
|
|
lock_acquire(&rcu_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_)
|
|
# define rcu_read_release() lock_release(&rcu_lock_map, 1, _THIS_IP_)
|
|
#else
|
|
# define rcu_read_acquire() do { } while (0)
|
|
# define rcu_read_release() do { } while (0)
|
|
#endif
|
|
|
|
/**
|
|
* rcu_read_lock - mark the beginning of an RCU read-side critical section.
|
|
*
|
|
* When synchronize_rcu() is invoked on one CPU while other CPUs
|
|
* are within RCU read-side critical sections, then the
|
|
* synchronize_rcu() is guaranteed to block until after all the other
|
|
* CPUs exit their critical sections. Similarly, if call_rcu() is invoked
|
|
* on one CPU while other CPUs are within RCU read-side critical
|
|
* sections, invocation of the corresponding RCU callback is deferred
|
|
* until after the all the other CPUs exit their critical sections.
|
|
*
|
|
* Note, however, that RCU callbacks are permitted to run concurrently
|
|
* with RCU read-side critical sections. One way that this can happen
|
|
* is via the following sequence of events: (1) CPU 0 enters an RCU
|
|
* read-side critical section, (2) CPU 1 invokes call_rcu() to register
|
|
* an RCU callback, (3) CPU 0 exits the RCU read-side critical section,
|
|
* (4) CPU 2 enters a RCU read-side critical section, (5) the RCU
|
|
* callback is invoked. This is legal, because the RCU read-side critical
|
|
* section that was running concurrently with the call_rcu() (and which
|
|
* therefore might be referencing something that the corresponding RCU
|
|
* callback would free up) has completed before the corresponding
|
|
* RCU callback is invoked.
|
|
*
|
|
* RCU read-side critical sections may be nested. Any deferred actions
|
|
* will be deferred until the outermost RCU read-side critical section
|
|
* completes.
|
|
*
|
|
* It is illegal to block while in an RCU read-side critical section.
|
|
*/
|
|
static inline void rcu_read_lock(void)
|
|
{
|
|
__rcu_read_lock();
|
|
__acquire(RCU);
|
|
rcu_read_acquire();
|
|
}
|
|
|
|
/*
|
|
* So where is rcu_write_lock()? It does not exist, as there is no
|
|
* way for writers to lock out RCU readers. This is a feature, not
|
|
* a bug -- this property is what provides RCU's performance benefits.
|
|
* Of course, writers must coordinate with each other. The normal
|
|
* spinlock primitives work well for this, but any other technique may be
|
|
* used as well. RCU does not care how the writers keep out of each
|
|
* others' way, as long as they do so.
|
|
*/
|
|
|
|
/**
|
|
* rcu_read_unlock - marks the end of an RCU read-side critical section.
|
|
*
|
|
* See rcu_read_lock() for more information.
|
|
*/
|
|
static inline void rcu_read_unlock(void)
|
|
{
|
|
rcu_read_release();
|
|
__release(RCU);
|
|
__rcu_read_unlock();
|
|
}
|
|
|
|
/**
|
|
* rcu_read_lock_bh - mark the beginning of a softirq-only RCU critical section
|
|
*
|
|
* This is equivalent of rcu_read_lock(), but to be used when updates
|
|
* are being done using call_rcu_bh(). Since call_rcu_bh() callbacks
|
|
* consider completion of a softirq handler to be a quiescent state,
|
|
* a process in RCU read-side critical section must be protected by
|
|
* disabling softirqs. Read-side critical sections in interrupt context
|
|
* can use just rcu_read_lock().
|
|
*
|
|
*/
|
|
static inline void rcu_read_lock_bh(void)
|
|
{
|
|
__rcu_read_lock_bh();
|
|
__acquire(RCU_BH);
|
|
rcu_read_acquire();
|
|
}
|
|
|
|
/*
|
|
* rcu_read_unlock_bh - marks the end of a softirq-only RCU critical section
|
|
*
|
|
* See rcu_read_lock_bh() for more information.
|
|
*/
|
|
static inline void rcu_read_unlock_bh(void)
|
|
{
|
|
rcu_read_release();
|
|
__release(RCU_BH);
|
|
__rcu_read_unlock_bh();
|
|
}
|
|
|
|
/**
|
|
* rcu_read_lock_sched - mark the beginning of a RCU-classic critical section
|
|
*
|
|
* Should be used with either
|
|
* - synchronize_sched()
|
|
* or
|
|
* - call_rcu_sched() and rcu_barrier_sched()
|
|
* on the write-side to insure proper synchronization.
|
|
*/
|
|
static inline void rcu_read_lock_sched(void)
|
|
{
|
|
preempt_disable();
|
|
__acquire(RCU_SCHED);
|
|
rcu_read_acquire();
|
|
}
|
|
|
|
/* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */
|
|
static inline notrace void rcu_read_lock_sched_notrace(void)
|
|
{
|
|
preempt_disable_notrace();
|
|
__acquire(RCU_SCHED);
|
|
}
|
|
|
|
/*
|
|
* rcu_read_unlock_sched - marks the end of a RCU-classic critical section
|
|
*
|
|
* See rcu_read_lock_sched for more information.
|
|
*/
|
|
static inline void rcu_read_unlock_sched(void)
|
|
{
|
|
rcu_read_release();
|
|
__release(RCU_SCHED);
|
|
preempt_enable();
|
|
}
|
|
|
|
/* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */
|
|
static inline notrace void rcu_read_unlock_sched_notrace(void)
|
|
{
|
|
__release(RCU_SCHED);
|
|
preempt_enable_notrace();
|
|
}
|
|
|
|
|
|
/**
|
|
* rcu_dereference - fetch an RCU-protected pointer in an
|
|
* RCU read-side critical section. This pointer may later
|
|
* be safely dereferenced.
|
|
*
|
|
* Inserts memory barriers on architectures that require them
|
|
* (currently only the Alpha), and, more importantly, documents
|
|
* exactly which pointers are protected by RCU.
|
|
*/
|
|
|
|
#define rcu_dereference(p) ({ \
|
|
typeof(p) _________p1 = ACCESS_ONCE(p); \
|
|
smp_read_barrier_depends(); \
|
|
(_________p1); \
|
|
})
|
|
|
|
/**
|
|
* rcu_assign_pointer - assign (publicize) a pointer to a newly
|
|
* initialized structure that will be dereferenced by RCU read-side
|
|
* critical sections. Returns the value assigned.
|
|
*
|
|
* Inserts memory barriers on architectures that require them
|
|
* (pretty much all of them other than x86), and also prevents
|
|
* the compiler from reordering the code that initializes the
|
|
* structure after the pointer assignment. More importantly, this
|
|
* call documents which pointers will be dereferenced by RCU read-side
|
|
* code.
|
|
*/
|
|
|
|
#define rcu_assign_pointer(p, v) \
|
|
({ \
|
|
if (!__builtin_constant_p(v) || \
|
|
((v) != NULL)) \
|
|
smp_wmb(); \
|
|
(p) = (v); \
|
|
})
|
|
|
|
/* Infrastructure to implement the synchronize_() primitives. */
|
|
|
|
struct rcu_synchronize {
|
|
struct rcu_head head;
|
|
struct completion completion;
|
|
};
|
|
|
|
extern void wakeme_after_rcu(struct rcu_head *head);
|
|
|
|
/**
|
|
* call_rcu - Queue an RCU callback for invocation after a grace period.
|
|
* @head: structure to be used for queueing the RCU updates.
|
|
* @func: actual update function to be invoked after the grace period
|
|
*
|
|
* The update function will be invoked some time after a full grace
|
|
* period elapses, in other words after all currently executing RCU
|
|
* read-side critical sections have completed. RCU read-side critical
|
|
* sections are delimited by rcu_read_lock() and rcu_read_unlock(),
|
|
* and may be nested.
|
|
*/
|
|
extern void call_rcu(struct rcu_head *head,
|
|
void (*func)(struct rcu_head *head));
|
|
|
|
/**
|
|
* call_rcu_bh - Queue an RCU for invocation after a quicker grace period.
|
|
* @head: structure to be used for queueing the RCU updates.
|
|
* @func: actual update function to be invoked after the grace period
|
|
*
|
|
* The update function will be invoked some time after a full grace
|
|
* period elapses, in other words after all currently executing RCU
|
|
* read-side critical sections have completed. call_rcu_bh() assumes
|
|
* that the read-side critical sections end on completion of a softirq
|
|
* handler. This means that read-side critical sections in process
|
|
* context must not be interrupted by softirqs. This interface is to be
|
|
* used when most of the read-side critical sections are in softirq context.
|
|
* RCU read-side critical sections are delimited by :
|
|
* - rcu_read_lock() and rcu_read_unlock(), if in interrupt context.
|
|
* OR
|
|
* - rcu_read_lock_bh() and rcu_read_unlock_bh(), if in process context.
|
|
* These may be nested.
|
|
*/
|
|
extern void call_rcu_bh(struct rcu_head *head,
|
|
void (*func)(struct rcu_head *head));
|
|
|
|
#endif /* __LINUX_RCUPDATE_H */
|