include/block/aio.h

   1 /*
   2  * QEMU aio implementation
   3  *
   4  * Copyright IBM, Corp. 2008
   5  *
   6  * Authors:
   7  *  Anthony Liguori   <aliguori@us.ibm.com>
   8  *
   9  * This work is licensed under the terms of the GNU GPL, version 2.  See
  10  * the COPYING file in the top-level directory.
  11  *
  12  */
  13
  14 #ifndef QEMU_AIO_H
  15 #define QEMU_AIO_H
  16
  17 #include "qemu/typedefs.h"
  18 #include "qemu-common.h"
  19 #include "qemu/queue.h"
  20 #include "qemu/event_notifier.h"
  21 #include "qemu/thread.h"
  22 #include "qemu/timer.h"
  23
  24 typedef struct BlockDriverAIOCB BlockDriverAIOCB;
  25 typedef void BlockDriverCompletionFunc(void *opaque, int ret);
  26
  27 typedef struct AIOCBInfo {
  28     void (*cancel)(BlockDriverAIOCB *acb);
  29     size_t aiocb_size;
  30 } AIOCBInfo;
  31
  32 struct BlockDriverAIOCB {
  33     const AIOCBInfo *aiocb_info;
  34     BlockDriverState *bs;
  35     BlockDriverCompletionFunc *cb;
  36     void *opaque;
  37 };
  38
  39 void *qemu_aio_get(const AIOCBInfo *aiocb_info, BlockDriverState *bs,
  40                    BlockDriverCompletionFunc *cb, void *opaque);
  41 void qemu_aio_release(void *p);
  42
  43 typedef struct AioHandler AioHandler;
  44 typedef void QEMUBHFunc(void *opaque);
  45 typedef void IOHandler(void *opaque);
  46
  47 struct AioContext {
  48     GSource source;
  49
  50     /* The list of registered AIO handlers */
  51     QLIST_HEAD(, AioHandler) aio_handlers;
  52
  53     /* This is a simple lock used to protect the aio_handlers list.
  54      * Specifically, it's used to ensure that no callbacks are removed while
  55      * we're walking and dispatching callbacks.
  56      */
  57     int walking_handlers;
  58
  59     /* lock to protect between bh's adders and deleter */
  60     QemuMutex bh_lock;
  61     /* Anchor of the list of Bottom Halves belonging to the context */
  62     struct QEMUBH *first_bh;
  63
  64     /* A simple lock used to protect the first_bh list, and ensure that
  65      * no callbacks are removed while we're walking and dispatching callbacks.
  66      */
  67     int walking_bh;
  68
  69     /* Used for aio_notify.  */
  70     EventNotifier notifier;
  71
  72     /* GPollFDs for aio_poll() */
  73     GArray *pollfds;
  74
  75     /* Thread pool for performing work and receiving completion callbacks */
  76     struct ThreadPool *thread_pool;
  77
  78     /* TimerLists for calling timers - one per clock type */
  79     QEMUTimerListGroup tlg;
  80 };
  81
  82 /**
  83  * aio_context_new: Allocate a new AioContext.
  84  *
  85  * AioContext provide a mini event-loop that can be waited on synchronously.
  86  * They also provide bottom halves, a service to execute a piece of code
  87  * as soon as possible.
  88  */
  89 AioContext *aio_context_new(void);
  90
  91 /**
  92  * aio_context_ref:
  93  * @ctx: The AioContext to operate on.
  94  *
  95  * Add a reference to an AioContext.
  96  */
  97 void aio_context_ref(AioContext *ctx);
  98
  99 /**
 100  * aio_context_unref:
 101  * @ctx: The AioContext to operate on.
 102  *
 103  * Drop a reference to an AioContext.
 104  */
 105 void aio_context_unref(AioContext *ctx);
 106
 107 /**
 108  * aio_bh_new: Allocate a new bottom half structure.
 109  *
 110  * Bottom halves are lightweight callbacks whose invocation is guaranteed
 111  * to be wait-free, thread-safe and signal-safe.  The #QEMUBH structure
 112  * is opaque and must be allocated prior to its use.
 113  */
 114 QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque);
 115
 116 /**
 117  * aio_notify: Force processing of pending events.
 118  *
 119  * Similar to signaling a condition variable, aio_notify forces
 120  * aio_wait to exit, so that the next call will re-examine pending events.
 121  * The caller of aio_notify will usually call aio_wait again very soon,
 122  * or go through another iteration of the GLib main loop.  Hence, aio_notify
 123  * also has the side effect of recalculating the sets of file descriptors
 124  * that the main loop waits for.
 125  *
 126  * Calling aio_notify is rarely necessary, because for example scheduling
 127  * a bottom half calls it already.
 128  */
 129 void aio_notify(AioContext *ctx);
 130
 131 /**
 132  * aio_bh_poll: Poll bottom halves for an AioContext.
 133  *
 134  * These are internal functions used by the QEMU main loop.
 135  * And notice that multiple occurrences of aio_bh_poll cannot
 136  * be called concurrently
 137  */
 138 int aio_bh_poll(AioContext *ctx);
 139
 140 /**
 141  * qemu_bh_schedule: Schedule a bottom half.
 142  *
 143  * Scheduling a bottom half interrupts the main loop and causes the
 144  * execution of the callback that was passed to qemu_bh_new.
 145  *
 146  * Bottom halves that are scheduled from a bottom half handler are instantly
 147  * invoked.  This can create an infinite loop if a bottom half handler
 148  * schedules itself.
 149  *
 150  * @bh: The bottom half to be scheduled.
 151  */
 152 void qemu_bh_schedule(QEMUBH *bh);
 153
 154 /**
 155  * qemu_bh_cancel: Cancel execution of a bottom half.
 156  *
 157  * Canceling execution of a bottom half undoes the effect of calls to
 158  * qemu_bh_schedule without freeing its resources yet.  While cancellation
 159  * itself is also wait-free and thread-safe, it can of course race with the
 160  * loop that executes bottom halves unless you are holding the iothread
 161  * mutex.  This makes it mostly useless if you are not holding the mutex.
 162  *
 163  * @bh: The bottom half to be canceled.
 164  */
 165 void qemu_bh_cancel(QEMUBH *bh);
 166
 167 /**
 168  *qemu_bh_delete: Cancel execution of a bottom half and free its resources.
 169  *
 170  * Deleting a bottom half frees the memory that was allocated for it by
 171  * qemu_bh_new.  It also implies canceling the bottom half if it was
 172  * scheduled.
 173  * This func is async. The bottom half will do the delete action at the finial
 174  * end.
 175  *
 176  * @bh: The bottom half to be deleted.
 177  */
 178 void qemu_bh_delete(QEMUBH *bh);
 179
 180 /* Return whether there are any pending callbacks from the GSource
 181  * attached to the AioContext.
 182  *
 183  * This is used internally in the implementation of the GSource.
 184  */
 185 bool aio_pending(AioContext *ctx);
 186
 187 /* Progress in completing AIO work to occur.  This can issue new pending
 188  * aio as a result of executing I/O completion or bh callbacks.
 189  *
 190  * If there is no pending AIO operation or completion (bottom half),
 191  * return false.  If there are pending AIO operations of bottom halves,
 192  * return true.
 193  *
 194  * If there are no pending bottom halves, but there are pending AIO
 195  * operations, it may not be possible to make any progress without
 196  * blocking.  If @blocking is true, this function will wait until one
 197  * or more AIO events have completed, to ensure something has moved
 198  * before returning.
 199  */
 200 bool aio_poll(AioContext *ctx, bool blocking);
 201
 202 #ifdef CONFIG_POSIX
 203 /* Register a file descriptor and associated callbacks.  Behaves very similarly
 204  * to qemu_set_fd_handler2.  Unlike qemu_set_fd_handler2, these callbacks will
 205  * be invoked when using qemu_aio_wait().
 206  *
 207  * Code that invokes AIO completion functions should rely on this function
 208  * instead of qemu_set_fd_handler[2].
 209  */
 210 void aio_set_fd_handler(AioContext *ctx,
 211                         int fd,
 212                         IOHandler *io_read,
 213                         IOHandler *io_write,
 214                         void *opaque);
 215 #endif
 216
 217 /* Register an event notifier and associated callbacks.  Behaves very similarly
 218  * to event_notifier_set_handler.  Unlike event_notifier_set_handler, these callbacks
 219  * will be invoked when using qemu_aio_wait().
 220  *
 221  * Code that invokes AIO completion functions should rely on this function
 222  * instead of event_notifier_set_handler.
 223  */
 224 void aio_set_event_notifier(AioContext *ctx,
 225                             EventNotifier *notifier,
 226                             EventNotifierHandler *io_read);
 227
 228 /* Return a GSource that lets the main loop poll the file descriptors attached
 229  * to this AioContext.
 230  */
 231 GSource *aio_get_g_source(AioContext *ctx);
 232
 233 /* Return the ThreadPool bound to this AioContext */
 234 struct ThreadPool *aio_get_thread_pool(AioContext *ctx);
 235
 236 /* Functions to operate on the main QEMU AioContext.  */
 237
 238 bool qemu_aio_wait(void);
 239 void qemu_aio_set_event_notifier(EventNotifier *notifier,
 240                                  EventNotifierHandler *io_read);
 241
 242 #ifdef CONFIG_POSIX
 243 void qemu_aio_set_fd_handler(int fd,
 244                              IOHandler *io_read,
 245                              IOHandler *io_write,
 246                              void *opaque);
 247 #endif
 248
 249 /**
 250  * aio_timer_new:
 251  * @ctx: the aio context
 252  * @type: the clock type
 253  * @scale: the scale
 254  * @cb: the callback to call on timer expiry
 255  * @opaque: the opaque pointer to pass to the callback
 256  *
 257  * Allocate a new timer attached to the context @ctx.
 258  * The function is responsible for memory allocation.
 259  *
 260  * The preferred interface is aio_timer_init. Use that
 261  * unless you really need dynamic memory allocation.
 262  *
 263  * Returns: a pointer to the new timer
 264  */
 265 static inline QEMUTimer *aio_timer_new(AioContext *ctx, QEMUClockType type,
 266                                        int scale,
 267                                        QEMUTimerCB *cb, void *opaque)
 268 {
 269     return timer_new_tl(ctx->tlg.tl[type], scale, cb, opaque);
 270 }
 271
 272 /**
 273  * aio_timer_init:
 274  * @ctx: the aio context
 275  * @ts: the timer
 276  * @type: the clock type
 277  * @scale: the scale
 278  * @cb: the callback to call on timer expiry
 279  * @opaque: the opaque pointer to pass to the callback
 280  *
 281  * Initialise a new timer attached to the context @ctx.
 282  * The caller is responsible for memory allocation.
 283  */
 284 static inline void aio_timer_init(AioContext *ctx,
 285                                   QEMUTimer *ts, QEMUClockType type,
 286                                   int scale,
 287                                   QEMUTimerCB *cb, void *opaque)
 288 {
 289     timer_init(ts, ctx->tlg.tl[type], scale, cb, opaque);
 290 }
 291
 292 #endif