win-pvdrivers

view common/include/public/io/ring.h @ 156:9a1f4acc38fb

Working on amd64 changes to try and get xenvbd to load properly. Fixed up the compiler warnings under x64 which were caused by public/io/ring.h.
author James Harper <james.harper@bendigoit.com.au>
date Fri Jan 25 13:36:43 2008 +1100 (2008-01-25)
parents 5712dede5a1b
children 6b41ede6aec5
line source
1 /******************************************************************************
2 * ring.h
3 *
4 * Shared producer-consumer ring macros.
5 *
6 * Permission is hereby granted, free of charge, to any person obtaining a copy
7 * of this software and associated documentation files (the "Software"), to
8 * deal in the Software without restriction, including without limitation the
9 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
10 * sell copies of the Software, and to permit persons to whom the Software is
11 * furnished to do so, subject to the following conditions:
12 *
13 * The above copyright notice and this permission notice shall be included in
14 * all copies or substantial portions of the Software.
15 *
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
19 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
21 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
22 * DEALINGS IN THE SOFTWARE.
23 *
24 * Tim Deegan and Andrew Warfield November 2004.
25 */
27 #ifndef __XEN_PUBLIC_IO_RING_H__
28 #define __XEN_PUBLIC_IO_RING_H__
30 typedef unsigned int RING_IDX;
32 /* Round a 32-bit unsigned constant down to the nearest power of two. */
33 #define __RD2(_x) (((_x) & 0x00000002) ? 0x2 : ((_x) & 0x1))
34 #define __RD4(_x) (((_x) & 0x0000000c) ? __RD2((_x)>>2)<<2 : __RD2(_x))
35 #define __RD8(_x) (((_x) & 0x000000f0) ? __RD4((_x)>>4)<<4 : __RD4(_x))
36 #define __RD16(_x) (((_x) & 0x0000ff00) ? __RD8((_x)>>8)<<8 : __RD8(_x))
37 #define __RD32(_x) (((_x) & 0xffff0000) ? __RD16((_x)>>16)<<16 : __RD16(_x))
39 /*
40 * Calculate size of a shared ring, given the total available space for the
41 * ring and indexes (_sz), and the name tag of the request/response structure.
42 * A ring contains as many entries as will fit, rounded down to the nearest
43 * power of two (so we can mask with (size-1) to loop around).
44 */
45 #define __RING_SIZE(_s, _sz) \
46 (__RD32(((_sz) - (long)(xen_ulong_t)(_s)->ring + (long)(xen_ulong_t)(_s)) / sizeof((_s)->ring[0])))
48 /*
49 * Macros to make the correct C datatypes for a new kind of ring.
50 *
51 * To make a new ring datatype, you need to have two message structures,
52 * let's say request_t, and response_t already defined.
53 *
54 * In a header where you want the ring datatype declared, you then do:
55 *
56 * DEFINE_RING_TYPES(mytag, request_t, response_t);
57 *
58 * These expand out to give you a set of types, as you can see below.
59 * The most important of these are:
60 *
61 * mytag_sring_t - The shared ring.
62 * mytag_front_ring_t - The 'front' half of the ring.
63 * mytag_back_ring_t - The 'back' half of the ring.
64 *
65 * To initialize a ring in your code you need to know the location and size
66 * of the shared memory area (PAGE_SIZE, for instance). To initialise
67 * the front half:
68 *
69 * mytag_front_ring_t front_ring;
70 * SHARED_RING_INIT((mytag_sring_t *)shared_page);
71 * FRONT_RING_INIT(&front_ring, (mytag_sring_t *)shared_page, PAGE_SIZE);
72 *
73 * Initializing the back follows similarly (note that only the front
74 * initializes the shared ring):
75 *
76 * mytag_back_ring_t back_ring;
77 * BACK_RING_INIT(&back_ring, (mytag_sring_t *)shared_page, PAGE_SIZE);
78 */
80 #define DEFINE_RING_TYPES(__name, __req_t, __rsp_t) \
81 \
82 /* Shared ring entry */ \
83 union __name##_sring_entry { \
84 __req_t req; \
85 __rsp_t rsp; \
86 }; \
87 \
88 /* Shared ring page */ \
89 struct __name##_sring { \
90 RING_IDX req_prod, req_event; \
91 RING_IDX rsp_prod, rsp_event; \
92 uint8_t pad[48]; \
93 union __name##_sring_entry ring[1]; /* variable-length */ \
94 }; \
95 \
96 /* "Front" end's private variables */ \
97 struct __name##_front_ring { \
98 RING_IDX req_prod_pvt; \
99 RING_IDX rsp_cons; \
100 unsigned int nr_ents; \
101 struct __name##_sring *sring; \
102 }; \
103 \
104 /* "Back" end's private variables */ \
105 struct __name##_back_ring { \
106 RING_IDX rsp_prod_pvt; \
107 RING_IDX req_cons; \
108 unsigned int nr_ents; \
109 struct __name##_sring *sring; \
110 }; \
111 \
112 /* Syntactic sugar */ \
113 typedef struct __name##_sring __name##_sring_t; \
114 typedef struct __name##_front_ring __name##_front_ring_t; \
115 typedef struct __name##_back_ring __name##_back_ring_t
117 /*
118 * Macros for manipulating rings.
119 *
120 * FRONT_RING_whatever works on the "front end" of a ring: here
121 * requests are pushed on to the ring and responses taken off it.
122 *
123 * BACK_RING_whatever works on the "back end" of a ring: here
124 * requests are taken off the ring and responses put on.
125 *
126 * N.B. these macros do NO INTERLOCKS OR FLOW CONTROL.
127 * This is OK in 1-for-1 request-response situations where the
128 * requestor (front end) never has more than RING_SIZE()-1
129 * outstanding requests.
130 */
132 /* Initialising empty rings */
133 #define SHARED_RING_INIT(_s) do { \
134 (_s)->req_prod = (_s)->rsp_prod = 0; \
135 (_s)->req_event = (_s)->rsp_event = 1; \
136 (void)memset((_s)->pad, 0, sizeof((_s)->pad)); \
137 } while(0)
139 #define FRONT_RING_INIT(_r, _s, __size) do { \
140 (_r)->req_prod_pvt = 0; \
141 (_r)->rsp_cons = 0; \
142 (_r)->nr_ents = __RING_SIZE(_s, __size); \
143 (_r)->sring = (_s); \
144 } while (0)
146 #define BACK_RING_INIT(_r, _s, __size) do { \
147 (_r)->rsp_prod_pvt = 0; \
148 (_r)->req_cons = 0; \
149 (_r)->nr_ents = __RING_SIZE(_s, __size); \
150 (_r)->sring = (_s); \
151 } while (0)
153 /* Initialize to existing shared indexes -- for recovery */
154 #define FRONT_RING_ATTACH(_r, _s, __size) do { \
155 (_r)->sring = (_s); \
156 (_r)->req_prod_pvt = (_s)->req_prod; \
157 (_r)->rsp_cons = (_s)->rsp_prod; \
158 (_r)->nr_ents = __RING_SIZE(_s, __size); \
159 } while (0)
161 #define BACK_RING_ATTACH(_r, _s, __size) do { \
162 (_r)->sring = (_s); \
163 (_r)->rsp_prod_pvt = (_s)->rsp_prod; \
164 (_r)->req_cons = (_s)->req_prod; \
165 (_r)->nr_ents = __RING_SIZE(_s, __size); \
166 } while (0)
168 /* How big is this ring? */
169 #define RING_SIZE(_r) \
170 ((_r)->nr_ents)
172 /* Number of free requests (for use on front side only). */
173 #define RING_FREE_REQUESTS(_r) \
174 (RING_SIZE(_r) - ((_r)->req_prod_pvt - (_r)->rsp_cons))
176 /* Test if there is an empty slot available on the front ring.
177 * (This is only meaningful from the front. )
178 */
179 #define RING_FULL(_r) \
180 (RING_FREE_REQUESTS(_r) == 0)
182 /* Test if there are outstanding messages to be processed on a ring. */
183 #define RING_HAS_UNCONSUMED_RESPONSES(_r) \
184 ((_r)->sring->rsp_prod - (_r)->rsp_cons)
186 #ifdef __GNUC__
187 #define RING_HAS_UNCONSUMED_REQUESTS(_r) ({ \
188 unsigned int req = (_r)->sring->req_prod - (_r)->req_cons; \
189 unsigned int rsp = RING_SIZE(_r) - \
190 ((_r)->req_cons - (_r)->rsp_prod_pvt); \
191 req < rsp ? req : rsp; \
192 })
193 #else
194 /* Same as above, but without the nice GCC ({ ... }) syntax. */
195 #define RING_HAS_UNCONSUMED_REQUESTS(_r) \
196 ((((_r)->sring->req_prod - (_r)->req_cons) < \
197 (RING_SIZE(_r) - ((_r)->req_cons - (_r)->rsp_prod_pvt))) ? \
198 ((_r)->sring->req_prod - (_r)->req_cons) : \
199 (RING_SIZE(_r) - ((_r)->req_cons - (_r)->rsp_prod_pvt)))
200 #endif
202 /* Direct access to individual ring elements, by index. */
203 #define RING_GET_REQUEST(_r, _idx) \
204 (&((_r)->sring->ring[((_idx) & (RING_SIZE(_r) - 1))].req))
206 #define RING_GET_RESPONSE(_r, _idx) \
207 (&((_r)->sring->ring[((_idx) & (RING_SIZE(_r) - 1))].rsp))
209 /* Loop termination condition: Would the specified index overflow the ring? */
210 #define RING_REQUEST_CONS_OVERFLOW(_r, _cons) \
211 (((_cons) - (_r)->rsp_prod_pvt) >= RING_SIZE(_r))
213 #define RING_PUSH_REQUESTS(_r) do { \
214 wmb(); /* back sees requests /before/ updated producer index */ \
215 (_r)->sring->req_prod = (_r)->req_prod_pvt; \
216 } while (0)
218 #define RING_PUSH_RESPONSES(_r) do { \
219 wmb(); /* front sees responses /before/ updated producer index */ \
220 (_r)->sring->rsp_prod = (_r)->rsp_prod_pvt; \
221 } while (0)
223 /*
224 * Notification hold-off (req_event and rsp_event):
225 *
226 * When queueing requests or responses on a shared ring, it may not always be
227 * necessary to notify the remote end. For example, if requests are in flight
228 * in a backend, the front may be able to queue further requests without
229 * notifying the back (if the back checks for new requests when it queues
230 * responses).
231 *
232 * When enqueuing requests or responses:
233 *
234 * Use RING_PUSH_{REQUESTS,RESPONSES}_AND_CHECK_NOTIFY(). The second argument
235 * is a boolean return value. True indicates that the receiver requires an
236 * asynchronous notification.
237 *
238 * After dequeuing requests or responses (before sleeping the connection):
239 *
240 * Use RING_FINAL_CHECK_FOR_REQUESTS() or RING_FINAL_CHECK_FOR_RESPONSES().
241 * The second argument is a boolean return value. True indicates that there
242 * are pending messages on the ring (i.e., the connection should not be put
243 * to sleep).
244 *
245 * These macros will set the req_event/rsp_event field to trigger a
246 * notification on the very next message that is enqueued. If you want to
247 * create batches of work (i.e., only receive a notification after several
248 * messages have been enqueued) then you will need to create a customised
249 * version of the FINAL_CHECK macro in your own code, which sets the event
250 * field appropriately.
251 */
253 #define RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(_r, _notify) do { \
254 RING_IDX __old = (_r)->sring->req_prod; \
255 RING_IDX __new = (_r)->req_prod_pvt; \
256 wmb(); /* back sees requests /before/ updated producer index */ \
257 (_r)->sring->req_prod = __new; \
258 mb(); /* back sees new requests /before/ we check req_event */ \
259 (_notify) = ((RING_IDX)(__new - (_r)->sring->req_event) < \
260 (RING_IDX)(__new - __old)); \
261 } while (0)
263 #define RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(_r, _notify) do { \
264 RING_IDX __old = (_r)->sring->rsp_prod; \
265 RING_IDX __new = (_r)->rsp_prod_pvt; \
266 wmb(); /* front sees responses /before/ updated producer index */ \
267 (_r)->sring->rsp_prod = __new; \
268 mb(); /* front sees new responses /before/ we check rsp_event */ \
269 (_notify) = ((RING_IDX)(__new - (_r)->sring->rsp_event) < \
270 (RING_IDX)(__new - __old)); \
271 } while (0)
273 #define RING_FINAL_CHECK_FOR_REQUESTS(_r, _work_to_do) do { \
274 (_work_to_do) = RING_HAS_UNCONSUMED_REQUESTS(_r); \
275 if (_work_to_do) break; \
276 (_r)->sring->req_event = (_r)->req_cons + 1; \
277 mb(); \
278 (_work_to_do) = RING_HAS_UNCONSUMED_REQUESTS(_r); \
279 } while (0)
281 #define RING_FINAL_CHECK_FOR_RESPONSES(_r, _work_to_do) do { \
282 (_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r); \
283 if (_work_to_do) break; \
284 (_r)->sring->rsp_event = (_r)->rsp_cons + 1; \
285 mb(); \
286 (_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r); \
287 } while (0)
289 #endif /* __XEN_PUBLIC_IO_RING_H__ */
291 /*
292 * Local variables:
293 * mode: C
294 * c-set-style: "BSD"
295 * c-basic-offset: 4
296 * tab-width: 4
297 * indent-tabs-mode: nil
298 * End:
299 */