include/linux/rcu_segcblist.h

Source file repositories/reference/linux-study-clean/include/linux/rcu_segcblist.h

File Facts

System
Linux kernel
Corpus path
include/linux/rcu_segcblist.h
Extension
.h
Size
11025 bytes
Lines
213
Domain
Core OS
Bucket
Core Kernel Interface
Inferred role
Core OS: implementation source
Status
source implementation candidate

Why This File Exists

Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.

Dependency Surface

Detected Declarations

Annotated Snippet

struct rcu_cblist {
	struct rcu_head *head;
	struct rcu_head **tail;
	long len;
};

#define RCU_CBLIST_INITIALIZER(n) { .head = NULL, .tail = &n.head }

/* Complicated segmented callback lists.  ;-) */

/*
 * Index values for segments in rcu_segcblist structure.
 *
 * The segments are as follows:
 *
 * [head, *tails[RCU_DONE_TAIL]):
 *	Callbacks whose grace period has elapsed, and thus can be invoked.
 * [*tails[RCU_DONE_TAIL], *tails[RCU_WAIT_TAIL]):
 *	Callbacks waiting for the current GP from the current CPU's viewpoint.
 * [*tails[RCU_WAIT_TAIL], *tails[RCU_NEXT_READY_TAIL]):
 *	Callbacks that arrived before the next GP started, again from
 *	the current CPU's viewpoint.  These can be handled by the next GP.
 * [*tails[RCU_NEXT_READY_TAIL], *tails[RCU_NEXT_TAIL]):
 *	Callbacks that might have arrived after the next GP started.
 *	There is some uncertainty as to when a given GP starts and
 *	ends, but a CPU knows the exact times if it is the one starting
 *	or ending the GP.  Other CPUs know that the previous GP ends
 *	before the next one starts.
 *
 * Note that RCU_WAIT_TAIL cannot be empty unless RCU_NEXT_READY_TAIL is also
 * empty.
 *
 * The ->gp_seq[] array contains the grace-period number at which the
 * corresponding segment of callbacks will be ready to invoke.  A given
 * element of this array is meaningful only when the corresponding segment
 * is non-empty, and it is never valid for RCU_DONE_TAIL (whose callbacks
 * are already ready to invoke) or for RCU_NEXT_TAIL (whose callbacks have
 * not yet been assigned a grace-period number).
 */
#define RCU_DONE_TAIL		0	/* Also RCU_WAIT head. */
#define RCU_WAIT_TAIL		1	/* Also RCU_NEXT_READY head. */
#define RCU_NEXT_READY_TAIL	2	/* Also RCU_NEXT head. */
#define RCU_NEXT_TAIL		3
#define RCU_CBLIST_NSEGS	4


/*
 *                     ==NOCB Offloading state machine==
 *
 *
 *  ----------------------------------------------------------------------------
 *  |                              SEGCBLIST_RCU_CORE                          |
 *  |                                                                          |
 *  |  Callbacks processed by rcu_core() from softirqs or local                |
 *  |  rcuc kthread, without holding nocb_lock.                                |
 *  ----------------------------------------------------------------------------
 *                                         |
 *                                         v
 *  ----------------------------------------------------------------------------
 *  |       SEGCBLIST_RCU_CORE | SEGCBLIST_LOCKING | SEGCBLIST_OFFLOADED       |
 *  |                                                                          |
 *  | Callbacks processed by rcu_core() from softirqs or local                 |
 *  | rcuc kthread, while holding nocb_lock. Waking up CB and GP kthreads.     |
 *  ----------------------------------------------------------------------------
 *                                         |
 *                                         v
 *  ----------------------------------------------------------------------------
 *  |        SEGCBLIST_RCU_CORE | SEGCBLIST_LOCKING | SEGCBLIST_OFFLOADED      |
 *  |                              + unparked CB kthread                       |
 *  |                                                                          |
 *  | CB kthread got unparked and processes callbacks concurrently with        |
 *  | rcu_core(), holding nocb_lock.                                           |
 *  ---------------------------------------------------------------------------
 *                                         |
 *                                         v
 *  ---------------------------------------------------------------------------|
 *  |                           SEGCBLIST_RCU_CORE |                           |
 *  |                           SEGCBLIST_LOCKING |                            |
 *  |                           SEGCBLIST_OFFLOADED |                          |
 *  |                           SEGCBLIST_KTHREAD_GP                           |
 *  |                           + unparked CB kthread                          |
 *  |                                                                          |
 *  | GP kthread woke up and acknowledged nocb_lock.                           |
 *  ---------------------------------------- -----------------------------------
 *                                         |
 *                                         v
 *  |--------------------------------------------------------------------------|
 *  |                           SEGCBLIST_LOCKING |                            |
 *  |                           SEGCBLIST_OFFLOADED |                          |
 *  |                           SEGCBLIST_KTHREAD_GP |                         |

Annotation

Implementation Notes