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484 lines
11 KiB
484 lines
11 KiB
/****************************************************************************** |
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* xenbus_comms.c |
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* |
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* Low level code to talks to Xen Store: ringbuffer and event channel. |
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* |
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* Copyright (C) 2005 Rusty Russell, IBM Corporation |
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* |
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* This program is free software; you can redistribute it and/or |
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* modify it under the terms of the GNU General Public License version 2 |
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* as published by the Free Software Foundation; or, when distributed |
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* separately from the Linux kernel or incorporated into other |
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* software packages, subject to the following license: |
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* |
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* Permission is hereby granted, free of charge, to any person obtaining a copy |
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* of this source file (the "Software"), to deal in the Software without |
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* restriction, including without limitation the rights to use, copy, modify, |
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* merge, publish, distribute, sublicense, and/or sell copies of the Software, |
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* and to permit persons to whom the Software is furnished to do so, subject to |
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* the following conditions: |
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* |
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* The above copyright notice and this permission notice shall be included in |
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* all copies or substantial portions of the Software. |
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* |
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING |
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS |
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* IN THE SOFTWARE. |
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*/ |
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
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#include <linux/wait.h> |
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#include <linux/interrupt.h> |
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#include <linux/kthread.h> |
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#include <linux/sched.h> |
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#include <linux/err.h> |
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#include <xen/xenbus.h> |
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#include <asm/xen/hypervisor.h> |
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#include <xen/events.h> |
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#include <xen/page.h> |
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#include "xenbus.h" |
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/* A list of replies. Currently only one will ever be outstanding. */ |
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LIST_HEAD(xs_reply_list); |
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/* A list of write requests. */ |
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LIST_HEAD(xb_write_list); |
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DECLARE_WAIT_QUEUE_HEAD(xb_waitq); |
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DEFINE_MUTEX(xb_write_mutex); |
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/* Protect xenbus reader thread against save/restore. */ |
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DEFINE_MUTEX(xs_response_mutex); |
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static int xenbus_irq; |
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static struct task_struct *xenbus_task; |
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static irqreturn_t wake_waiting(int irq, void *unused) |
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{ |
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wake_up(&xb_waitq); |
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return IRQ_HANDLED; |
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} |
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static int check_indexes(XENSTORE_RING_IDX cons, XENSTORE_RING_IDX prod) |
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{ |
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return ((prod - cons) <= XENSTORE_RING_SIZE); |
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} |
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static void *get_output_chunk(XENSTORE_RING_IDX cons, |
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XENSTORE_RING_IDX prod, |
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char *buf, uint32_t *len) |
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{ |
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*len = XENSTORE_RING_SIZE - MASK_XENSTORE_IDX(prod); |
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if ((XENSTORE_RING_SIZE - (prod - cons)) < *len) |
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*len = XENSTORE_RING_SIZE - (prod - cons); |
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return buf + MASK_XENSTORE_IDX(prod); |
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} |
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static const void *get_input_chunk(XENSTORE_RING_IDX cons, |
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XENSTORE_RING_IDX prod, |
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const char *buf, uint32_t *len) |
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{ |
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*len = XENSTORE_RING_SIZE - MASK_XENSTORE_IDX(cons); |
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if ((prod - cons) < *len) |
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*len = prod - cons; |
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return buf + MASK_XENSTORE_IDX(cons); |
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} |
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static int xb_data_to_write(void) |
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{ |
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struct xenstore_domain_interface *intf = xen_store_interface; |
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return (intf->req_prod - intf->req_cons) != XENSTORE_RING_SIZE && |
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!list_empty(&xb_write_list); |
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} |
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/** |
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* xb_write - low level write |
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* @data: buffer to send |
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* @len: length of buffer |
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* |
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* Returns number of bytes written or -err. |
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*/ |
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static int xb_write(const void *data, unsigned int len) |
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{ |
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struct xenstore_domain_interface *intf = xen_store_interface; |
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XENSTORE_RING_IDX cons, prod; |
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unsigned int bytes = 0; |
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while (len != 0) { |
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void *dst; |
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unsigned int avail; |
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/* Read indexes, then verify. */ |
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cons = intf->req_cons; |
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prod = intf->req_prod; |
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if (!check_indexes(cons, prod)) { |
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intf->req_cons = intf->req_prod = 0; |
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return -EIO; |
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} |
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if (!xb_data_to_write()) |
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return bytes; |
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/* Must write data /after/ reading the consumer index. */ |
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virt_mb(); |
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dst = get_output_chunk(cons, prod, intf->req, &avail); |
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if (avail == 0) |
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continue; |
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if (avail > len) |
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avail = len; |
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memcpy(dst, data, avail); |
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data += avail; |
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len -= avail; |
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bytes += avail; |
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/* Other side must not see new producer until data is there. */ |
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virt_wmb(); |
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intf->req_prod += avail; |
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/* Implies mb(): other side will see the updated producer. */ |
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if (prod <= intf->req_cons) |
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notify_remote_via_evtchn(xen_store_evtchn); |
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} |
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return bytes; |
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} |
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static int xb_data_to_read(void) |
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{ |
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struct xenstore_domain_interface *intf = xen_store_interface; |
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return (intf->rsp_cons != intf->rsp_prod); |
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} |
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static int xb_read(void *data, unsigned int len) |
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{ |
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struct xenstore_domain_interface *intf = xen_store_interface; |
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XENSTORE_RING_IDX cons, prod; |
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unsigned int bytes = 0; |
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while (len != 0) { |
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unsigned int avail; |
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const char *src; |
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/* Read indexes, then verify. */ |
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cons = intf->rsp_cons; |
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prod = intf->rsp_prod; |
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if (cons == prod) |
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return bytes; |
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if (!check_indexes(cons, prod)) { |
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intf->rsp_cons = intf->rsp_prod = 0; |
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return -EIO; |
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} |
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src = get_input_chunk(cons, prod, intf->rsp, &avail); |
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if (avail == 0) |
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continue; |
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if (avail > len) |
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avail = len; |
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/* Must read data /after/ reading the producer index. */ |
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virt_rmb(); |
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memcpy(data, src, avail); |
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data += avail; |
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len -= avail; |
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bytes += avail; |
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/* Other side must not see free space until we've copied out */ |
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virt_mb(); |
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intf->rsp_cons += avail; |
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/* Implies mb(): other side will see the updated consumer. */ |
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if (intf->rsp_prod - cons >= XENSTORE_RING_SIZE) |
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notify_remote_via_evtchn(xen_store_evtchn); |
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} |
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return bytes; |
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} |
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static int process_msg(void) |
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{ |
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static struct { |
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struct xsd_sockmsg msg; |
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char *body; |
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union { |
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void *alloc; |
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struct xs_watch_event *watch; |
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}; |
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bool in_msg; |
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bool in_hdr; |
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unsigned int read; |
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} state; |
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struct xb_req_data *req; |
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int err; |
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unsigned int len; |
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if (!state.in_msg) { |
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state.in_msg = true; |
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state.in_hdr = true; |
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state.read = 0; |
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/* |
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* We must disallow save/restore while reading a message. |
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* A partial read across s/r leaves us out of sync with |
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* xenstored. |
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* xs_response_mutex is locked as long as we are processing one |
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* message. state.in_msg will be true as long as we are holding |
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* the lock here. |
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*/ |
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mutex_lock(&xs_response_mutex); |
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if (!xb_data_to_read()) { |
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/* We raced with save/restore: pending data 'gone'. */ |
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mutex_unlock(&xs_response_mutex); |
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state.in_msg = false; |
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return 0; |
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} |
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} |
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if (state.in_hdr) { |
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if (state.read != sizeof(state.msg)) { |
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err = xb_read((void *)&state.msg + state.read, |
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sizeof(state.msg) - state.read); |
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if (err < 0) |
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goto out; |
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state.read += err; |
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if (state.read != sizeof(state.msg)) |
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return 0; |
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if (state.msg.len > XENSTORE_PAYLOAD_MAX) { |
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err = -EINVAL; |
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goto out; |
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} |
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} |
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len = state.msg.len + 1; |
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if (state.msg.type == XS_WATCH_EVENT) |
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len += sizeof(*state.watch); |
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state.alloc = kmalloc(len, GFP_NOIO | __GFP_HIGH); |
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if (!state.alloc) |
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return -ENOMEM; |
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if (state.msg.type == XS_WATCH_EVENT) |
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state.body = state.watch->body; |
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else |
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state.body = state.alloc; |
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state.in_hdr = false; |
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state.read = 0; |
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} |
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err = xb_read(state.body + state.read, state.msg.len - state.read); |
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if (err < 0) |
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goto out; |
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state.read += err; |
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if (state.read != state.msg.len) |
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return 0; |
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state.body[state.msg.len] = '\0'; |
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if (state.msg.type == XS_WATCH_EVENT) { |
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state.watch->len = state.msg.len; |
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err = xs_watch_msg(state.watch); |
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} else { |
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err = -ENOENT; |
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mutex_lock(&xb_write_mutex); |
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list_for_each_entry(req, &xs_reply_list, list) { |
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if (req->msg.req_id == state.msg.req_id) { |
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list_del(&req->list); |
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err = 0; |
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break; |
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} |
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} |
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mutex_unlock(&xb_write_mutex); |
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if (err) |
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goto out; |
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if (req->state == xb_req_state_wait_reply) { |
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req->msg.req_id = req->caller_req_id; |
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req->msg.type = state.msg.type; |
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req->msg.len = state.msg.len; |
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req->body = state.body; |
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/* write body, then update state */ |
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virt_wmb(); |
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req->state = xb_req_state_got_reply; |
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req->cb(req); |
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} else |
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kfree(req); |
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} |
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mutex_unlock(&xs_response_mutex); |
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state.in_msg = false; |
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state.alloc = NULL; |
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return err; |
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out: |
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mutex_unlock(&xs_response_mutex); |
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state.in_msg = false; |
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kfree(state.alloc); |
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state.alloc = NULL; |
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return err; |
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} |
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static int process_writes(void) |
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{ |
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static struct { |
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struct xb_req_data *req; |
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int idx; |
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unsigned int written; |
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} state; |
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void *base; |
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unsigned int len; |
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int err = 0; |
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if (!xb_data_to_write()) |
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return 0; |
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mutex_lock(&xb_write_mutex); |
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if (!state.req) { |
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state.req = list_first_entry(&xb_write_list, |
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struct xb_req_data, list); |
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state.idx = -1; |
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state.written = 0; |
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} |
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if (state.req->state == xb_req_state_aborted) |
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goto out_err; |
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while (state.idx < state.req->num_vecs) { |
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if (state.idx < 0) { |
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base = &state.req->msg; |
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len = sizeof(state.req->msg); |
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} else { |
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base = state.req->vec[state.idx].iov_base; |
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len = state.req->vec[state.idx].iov_len; |
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} |
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err = xb_write(base + state.written, len - state.written); |
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if (err < 0) |
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goto out_err; |
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state.written += err; |
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if (state.written != len) |
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goto out; |
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state.idx++; |
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state.written = 0; |
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} |
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list_del(&state.req->list); |
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state.req->state = xb_req_state_wait_reply; |
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list_add_tail(&state.req->list, &xs_reply_list); |
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state.req = NULL; |
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out: |
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mutex_unlock(&xb_write_mutex); |
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return 0; |
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out_err: |
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state.req->msg.type = XS_ERROR; |
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state.req->err = err; |
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list_del(&state.req->list); |
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if (state.req->state == xb_req_state_aborted) |
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kfree(state.req); |
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else { |
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/* write err, then update state */ |
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virt_wmb(); |
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state.req->state = xb_req_state_got_reply; |
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wake_up(&state.req->wq); |
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} |
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mutex_unlock(&xb_write_mutex); |
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state.req = NULL; |
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return err; |
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} |
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static int xb_thread_work(void) |
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{ |
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return xb_data_to_read() || xb_data_to_write(); |
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} |
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static int xenbus_thread(void *unused) |
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{ |
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int err; |
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while (!kthread_should_stop()) { |
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if (wait_event_interruptible(xb_waitq, xb_thread_work())) |
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continue; |
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err = process_msg(); |
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if (err == -ENOMEM) |
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schedule(); |
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else if (err) |
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pr_warn_ratelimited("error %d while reading message\n", |
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err); |
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err = process_writes(); |
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if (err) |
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pr_warn_ratelimited("error %d while writing message\n", |
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err); |
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} |
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xenbus_task = NULL; |
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return 0; |
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} |
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/** |
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* xb_init_comms - Set up interrupt handler off store event channel. |
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*/ |
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int xb_init_comms(void) |
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{ |
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struct xenstore_domain_interface *intf = xen_store_interface; |
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if (intf->req_prod != intf->req_cons) |
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pr_err("request ring is not quiescent (%08x:%08x)!\n", |
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intf->req_cons, intf->req_prod); |
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if (intf->rsp_prod != intf->rsp_cons) { |
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pr_warn("response ring is not quiescent (%08x:%08x): fixing up\n", |
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intf->rsp_cons, intf->rsp_prod); |
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/* breaks kdump */ |
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if (!reset_devices) |
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intf->rsp_cons = intf->rsp_prod; |
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} |
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if (xenbus_irq) { |
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/* Already have an irq; assume we're resuming */ |
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rebind_evtchn_irq(xen_store_evtchn, xenbus_irq); |
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} else { |
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int err; |
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err = bind_evtchn_to_irqhandler(xen_store_evtchn, wake_waiting, |
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0, "xenbus", &xb_waitq); |
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if (err < 0) { |
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pr_err("request irq failed %i\n", err); |
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return err; |
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} |
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xenbus_irq = err; |
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if (!xenbus_task) { |
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xenbus_task = kthread_run(xenbus_thread, NULL, |
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"xenbus"); |
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if (IS_ERR(xenbus_task)) |
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return PTR_ERR(xenbus_task); |
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} |
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} |
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return 0; |
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} |
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void xb_deinit_comms(void) |
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{ |
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unbind_from_irqhandler(xenbus_irq, &xb_waitq); |
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xenbus_irq = 0; |
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}
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