| /****************************************************************************** |
| * ring.h |
| * |
| * Shared producer-consumer ring macros. |
| * |
| * Permission is hereby granted, free of charge, to any person obtaining a copy |
| * of this software and associated documentation files (the "Software"), to |
| * deal in the Software without restriction, including without limitation the |
| * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or |
| * sell copies of the Software, and to permit persons to whom the Software is |
| * furnished to do so, subject to the following conditions: |
| * |
| * The above copyright notice and this permission notice shall be included in |
| * all copies or substantial portions of the Software. |
| * |
| * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
| * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
| * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
| * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING |
| * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER |
| * DEALINGS IN THE SOFTWARE. |
| * |
| * Tim Deegan and Andrew Warfield November 2004. |
| */ |
| |
| #pragma once |
| #include <string.h> |
| #include <ros/arch/membar.h> |
| |
| #define xen_mb() mb() |
| #define xen_rmb() rmb() |
| #define xen_wmb() wmb() |
| |
| /* Helpers for generic power-of-2 ring buffers */ |
| #define __ring_nr_empty(sz, prod, cons) ((sz) - ((prod) - (cons))) |
| #define __ring_empty(prod, cons) ((prod) == (cons)) |
| #define __ring_nr_full(prod, cons) ((prod) - (cons)) |
| #define __ring_full(sz, prod, cons) (__ring_nr_empty((sz), (prod), (cons)) == 0) |
| |
| typedef unsigned int RING_IDX; |
| |
| /* Round a 32-bit unsigned constant down to the nearest power of two. */ |
| #define __RD2(_x) (((_x) & 0x00000002UL) ? 0x2 : ((_x) & 0x1)) |
| #define __RD4(_x) (((_x) & 0x0000000cUL) ? __RD2((_x)>>2)<<2 : __RD2(_x)) |
| #define __RD8(_x) (((_x) & 0x000000f0UL) ? __RD4((_x)>>4)<<4 : __RD4(_x)) |
| #define __RD16(_x) (((_x) & 0x0000ff00UL) ? __RD8((_x)>>8)<<8 : __RD8(_x)) |
| #define __RD32(_x) (((_x) & 0xffff0000UL) ? __RD16((_x)>>16)<<16 : __RD16(_x)) |
| |
| /* |
| * Calculate size of a shared ring, given the total available space for the |
| * ring and indexes (_sz), and the name tag of the request/response structure. |
| * A ring contains as many entries as will fit, rounded down to the nearest |
| * power of two (so we can mask with (size-1) to loop around). |
| */ |
| #define __CONST_RING_SIZE(_s, _sz) \ |
| (__RD32(((_sz) - offsetof(struct _s##_sring, ring)) / \ |
| sizeof(((struct _s##_sring *)0)->ring[0]))) |
| /* |
| * The same for passing in an actual pointer instead of a name tag. |
| */ |
| #define __RING_SIZE(_s, _sz) \ |
| (__RD32(((_sz) - (long)(_s)->ring + (long)(_s)) / sizeof((_s)->ring[0]))) |
| |
| /* |
| * Macros to make the correct C datatypes for a new kind of ring. |
| * |
| * To make a new ring datatype, you need to have two message structures, |
| * let's say request_t, and response_t already defined. |
| * |
| * In a header where you want the ring datatype declared, you then do: |
| * |
| * DEFINE_RING_TYPES(mytag, request_t, response_t); |
| * |
| * These expand out to give you a set of types, as you can see below. |
| * The most important of these are: |
| * |
| * mytag_sring_t - The shared ring. |
| * mytag_front_ring_t - The 'front' half of the ring. |
| * mytag_back_ring_t - The 'back' half of the ring. |
| * |
| * To initialize a ring in your code you need to know the location and size |
| * of the shared memory area (PAGE_SIZE, for instance). To initialise |
| * the front half: |
| * |
| * mytag_front_ring_t front_ring; |
| * SHARED_RING_INIT((mytag_sring_t *)shared_page); |
| * FRONT_RING_INIT(&front_ring, (mytag_sring_t *)shared_page, PAGE_SIZE); |
| * |
| * Initializing the back follows similarly (note that only the front |
| * initializes the shared ring): |
| * |
| * mytag_back_ring_t back_ring; |
| * BACK_RING_INIT(&back_ring, (mytag_sring_t *)shared_page, PAGE_SIZE); |
| */ |
| |
| #define DEFINE_RING_TYPES(__name, __req_t, __rsp_t) \ |
| \ |
| /* Shared ring entry */ \ |
| union __name##_sring_entry { \ |
| __req_t req; \ |
| __rsp_t rsp; \ |
| }; \ |
| \ |
| /* Shared ring page */ \ |
| struct __name##_sring { \ |
| RING_IDX req_prod, req_event; \ |
| RING_IDX rsp_prod, rsp_event; \ |
| union { \ |
| struct { \ |
| uint8_t smartpoll_active; \ |
| } netif; \ |
| struct { \ |
| uint8_t msg; \ |
| } tapif_user; \ |
| uint8_t pvt_pad[4]; \ |
| } priv; \ |
| uint8_t __pad[44]; \ |
| union __name##_sring_entry ring[1]; /* variable-length */ \ |
| }; \ |
| \ |
| /* "Front" end's private variables */ \ |
| struct __name##_front_ring { \ |
| RING_IDX req_prod_pvt; \ |
| RING_IDX rsp_cons; \ |
| unsigned int nr_ents; \ |
| struct __name##_sring *sring; \ |
| }; \ |
| \ |
| /* "Back" end's private variables */ \ |
| struct __name##_back_ring { \ |
| RING_IDX rsp_prod_pvt; \ |
| RING_IDX req_cons; \ |
| unsigned int nr_ents; \ |
| struct __name##_sring *sring; \ |
| }; \ |
| \ |
| /* Syntactic sugar */ \ |
| typedef struct __name##_sring __name##_sring_t; \ |
| typedef struct __name##_front_ring __name##_front_ring_t; \ |
| typedef struct __name##_back_ring __name##_back_ring_t |
| |
| /* |
| * Macros for manipulating rings. |
| * |
| * FRONT_RING_whatever works on the "front end" of a ring: here |
| * requests are pushed on to the ring and responses taken off it. |
| * |
| * BACK_RING_whatever works on the "back end" of a ring: here |
| * requests are taken off the ring and responses put on. |
| * |
| * N.B. these macros do NO INTERLOCKS OR FLOW CONTROL. |
| * This is OK in 1-for-1 request-response situations where the |
| * requestor (front end) never has more than RING_SIZE()-1 |
| * outstanding requests. |
| */ |
| |
| /* Initialising empty rings */ |
| #define SHARED_RING_INIT(_s) do { \ |
| (_s)->req_prod = (_s)->rsp_prod = 0; \ |
| (_s)->req_event = (_s)->rsp_event = 1; \ |
| (void)memset((_s)->priv.pvt_pad, 0, sizeof((_s)->priv.pvt_pad)); \ |
| (void)memset((_s)->__pad, 0, sizeof((_s)->__pad)); \ |
| } while(0) |
| |
| #define FRONT_RING_INIT(_r, _s, __size) do { \ |
| (_r)->req_prod_pvt = 0; \ |
| (_r)->rsp_cons = 0; \ |
| (_r)->nr_ents = __RING_SIZE(_s, __size); \ |
| (_r)->sring = (_s); \ |
| } while (0) |
| |
| #define BACK_RING_INIT(_r, _s, __size) do { \ |
| (_r)->rsp_prod_pvt = 0; \ |
| (_r)->req_cons = 0; \ |
| (_r)->nr_ents = __RING_SIZE(_s, __size); \ |
| (_r)->sring = (_s); \ |
| } while (0) |
| |
| /* Initialize to existing shared indexes -- for recovery */ |
| #define FRONT_RING_ATTACH(_r, _s, __size) do { \ |
| (_r)->sring = (_s); \ |
| (_r)->req_prod_pvt = (_s)->req_prod; \ |
| (_r)->rsp_cons = (_s)->rsp_prod; \ |
| (_r)->nr_ents = __RING_SIZE(_s, __size); \ |
| } while (0) |
| |
| #define BACK_RING_ATTACH(_r, _s, __size) do { \ |
| (_r)->sring = (_s); \ |
| (_r)->rsp_prod_pvt = (_s)->rsp_prod; \ |
| (_r)->req_cons = (_s)->req_prod; \ |
| (_r)->nr_ents = __RING_SIZE(_s, __size); \ |
| } while (0) |
| |
| /* How big is this ring? */ |
| #define RING_SIZE(_r) \ |
| ((_r)->nr_ents) |
| |
| /* Number of free requests (for use on front side only). */ |
| #define RING_FREE_REQUESTS(_r) \ |
| (RING_SIZE(_r) - ((_r)->req_prod_pvt - (_r)->rsp_cons)) |
| |
| /* Test if there is an empty slot available on the front ring. |
| * (This is only meaningful from the front. ) |
| */ |
| #define RING_FULL(_r) \ |
| (RING_FREE_REQUESTS(_r) == 0) |
| |
| /* Test if there are outstanding messages to be processed on a ring. */ |
| #define RING_HAS_UNCONSUMED_RESPONSES(_r) \ |
| ((_r)->sring->rsp_prod - (_r)->rsp_cons) |
| |
| #ifdef __GNUC__ |
| #define RING_HAS_UNCONSUMED_REQUESTS(_r) ({ \ |
| unsigned int req = (_r)->sring->req_prod - (_r)->req_cons; \ |
| unsigned int rsp = RING_SIZE(_r) - \ |
| ((_r)->req_cons - (_r)->rsp_prod_pvt); \ |
| req < rsp ? req : rsp; \ |
| }) |
| #else |
| /* Same as above, but without the nice GCC ({ ... }) syntax. */ |
| #define RING_HAS_UNCONSUMED_REQUESTS(_r) \ |
| ((((_r)->sring->req_prod - (_r)->req_cons) < \ |
| (RING_SIZE(_r) - ((_r)->req_cons - (_r)->rsp_prod_pvt))) ? \ |
| ((_r)->sring->req_prod - (_r)->req_cons) : \ |
| (RING_SIZE(_r) - ((_r)->req_cons - (_r)->rsp_prod_pvt))) |
| #endif |
| |
| /* Direct access to individual ring elements, by index. */ |
| #define RING_GET_REQUEST(_r, _idx) \ |
| (&((_r)->sring->ring[((_idx) & (RING_SIZE(_r) - 1))].req)) |
| |
| #define RING_GET_RESPONSE(_r, _idx) \ |
| (&((_r)->sring->ring[((_idx) & (RING_SIZE(_r) - 1))].rsp)) |
| |
| /* Loop termination condition: Would the specified index overflow the ring? */ |
| #define RING_REQUEST_CONS_OVERFLOW(_r, _cons) \ |
| (((_cons) - (_r)->rsp_prod_pvt) >= RING_SIZE(_r)) |
| |
| #define RING_PUSH_REQUESTS(_r) do { \ |
| xen_wmb(); /* back sees requests /before/ updated producer index */ \ |
| (_r)->sring->req_prod = (_r)->req_prod_pvt; \ |
| } while (0) |
| |
| #define RING_PUSH_RESPONSES(_r) do { \ |
| xen_wmb(); /* front sees resps /before/ updated producer index */ \ |
| (_r)->sring->rsp_prod = (_r)->rsp_prod_pvt; \ |
| } while (0) |
| |
| /* |
| * Notification hold-off (req_event and rsp_event): |
| * |
| * When queueing requests or responses on a shared ring, it may not always be |
| * necessary to notify the remote end. For example, if requests are in flight |
| * in a backend, the front may be able to queue further requests without |
| * notifying the back (if the back checks for new requests when it queues |
| * responses). |
| * |
| * When enqueuing requests or responses: |
| * |
| * Use RING_PUSH_{REQUESTS,RESPONSES}_AND_CHECK_NOTIFY(). The second argument |
| * is a boolean return value. True indicates that the receiver requires an |
| * asynchronous notification. |
| * |
| * After dequeuing requests or responses (before sleeping the connection): |
| * |
| * Use RING_FINAL_CHECK_FOR_REQUESTS() or RING_FINAL_CHECK_FOR_RESPONSES(). |
| * The second argument is a boolean return value. True indicates that there |
| * are pending messages on the ring (i.e., the connection should not be put |
| * to sleep). |
| * |
| * These macros will set the req_event/rsp_event field to trigger a |
| * notification on the very next message that is enqueued. If you want to |
| * create batches of work (i.e., only receive a notification after several |
| * messages have been enqueued) then you will need to create a customised |
| * version of the FINAL_CHECK macro in your own code, which sets the event |
| * field appropriately. |
| */ |
| |
| #define RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(_r, _notify) do { \ |
| RING_IDX __old = (_r)->sring->req_prod; \ |
| RING_IDX __new = (_r)->req_prod_pvt; \ |
| xen_wmb(); /* back sees requests /before/ updated producer index */ \ |
| (_r)->sring->req_prod = __new; \ |
| xen_mb(); /* back sees new requests /before/ we check req_event */ \ |
| (_notify) = ((RING_IDX)(__new - (_r)->sring->req_event) < \ |
| (RING_IDX)(__new - __old)); \ |
| } while (0) |
| |
| #define RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(_r, _notify) do { \ |
| RING_IDX __old = (_r)->sring->rsp_prod; \ |
| RING_IDX __new = (_r)->rsp_prod_pvt; \ |
| xen_wmb(); /* front sees resps /before/ updated producer index */ \ |
| (_r)->sring->rsp_prod = __new; \ |
| xen_mb(); /* front sees new resps /before/ we check rsp_event */ \ |
| (_notify) = ((RING_IDX)(__new - (_r)->sring->rsp_event) < \ |
| (RING_IDX)(__new - __old)); \ |
| } while (0) |
| |
| #define RING_FINAL_CHECK_FOR_REQUESTS(_r, _work_to_do) do { \ |
| (_work_to_do) = RING_HAS_UNCONSUMED_REQUESTS(_r); \ |
| if (_work_to_do) break; \ |
| (_r)->sring->req_event = (_r)->req_cons + 1; \ |
| xen_mb(); \ |
| (_work_to_do) = RING_HAS_UNCONSUMED_REQUESTS(_r); \ |
| } while (0) |
| |
| #define RING_FINAL_CHECK_FOR_RESPONSES(_r, _work_to_do) do { \ |
| (_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r); \ |
| if (_work_to_do) break; \ |
| (_r)->sring->rsp_event = (_r)->rsp_cons + 1; \ |
| xen_mb(); \ |
| (_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r); \ |
| } while (0) |
| |
| /* |
| * Local variables: |
| * mode: C |
| * c-set-style: "BSD" |
| * c-basic-offset: 4 |
| * tab-width: 4 |
| * indent-tabs-mode: nil |
| * End: |
| */ |
