diff options
Diffstat (limited to 'drivers/xen/xenbus/xenbus_xs.c')
| -rw-r--r-- | drivers/xen/xenbus/xenbus_xs.c | 956 |
1 files changed, 956 insertions, 0 deletions
diff --git a/drivers/xen/xenbus/xenbus_xs.c b/drivers/xen/xenbus/xenbus_xs.c new file mode 100644 index 000000000..12e02eb01 --- /dev/null +++ b/drivers/xen/xenbus/xenbus_xs.c @@ -0,0 +1,956 @@ +/****************************************************************************** + * xenbus_xs.c + * + * This is the kernel equivalent of the "xs" library. We don't need everything + * and we use xenbus_comms for communication. + * + * Copyright (C) 2005 Rusty Russell, IBM Corporation + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License version 2 + * as published by the Free Software Foundation; or, when distributed + * separately from the Linux kernel or incorporated into other + * software packages, subject to the following license: + * + * Permission is hereby granted, free of charge, to any person obtaining a copy + * of this source file (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. + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/unistd.h> +#include <linux/errno.h> +#include <linux/types.h> +#include <linux/uio.h> +#include <linux/kernel.h> +#include <linux/string.h> +#include <linux/err.h> +#include <linux/slab.h> +#include <linux/fcntl.h> +#include <linux/kthread.h> +#include <linux/reboot.h> +#include <linux/rwsem.h> +#include <linux/mutex.h> +#include <asm/xen/hypervisor.h> +#include <xen/xenbus.h> +#include <xen/xen.h> +#include "xenbus.h" + +/* + * Framework to protect suspend/resume handling against normal Xenstore + * message handling: + * During suspend/resume there must be no open transaction and no pending + * Xenstore request. + * New watch events happening in this time can be ignored by firing all watches + * after resume. + */ + +/* Lock protecting enter/exit critical region. */ +static DEFINE_SPINLOCK(xs_state_lock); +/* Number of users in critical region (protected by xs_state_lock). */ +static unsigned int xs_state_users; +/* Suspend handler waiting or already active (protected by xs_state_lock)? */ +static int xs_suspend_active; +/* Unique Xenstore request id (protected by xs_state_lock). */ +static uint32_t xs_request_id; + +/* Wait queue for all callers waiting for critical region to become usable. */ +static DECLARE_WAIT_QUEUE_HEAD(xs_state_enter_wq); +/* Wait queue for suspend handling waiting for critical region being empty. */ +static DECLARE_WAIT_QUEUE_HEAD(xs_state_exit_wq); + +/* List of registered watches, and a lock to protect it. */ +static LIST_HEAD(watches); +static DEFINE_SPINLOCK(watches_lock); + +/* List of pending watch callback events, and a lock to protect it. */ +static LIST_HEAD(watch_events); +static DEFINE_SPINLOCK(watch_events_lock); + +/* Protect watch (de)register against save/restore. */ +static DECLARE_RWSEM(xs_watch_rwsem); + +/* + * Details of the xenwatch callback kernel thread. The thread waits on the + * watch_events_waitq for work to do (queued on watch_events list). When it + * wakes up it acquires the xenwatch_mutex before reading the list and + * carrying out work. + */ +static pid_t xenwatch_pid; +static DEFINE_MUTEX(xenwatch_mutex); +static DECLARE_WAIT_QUEUE_HEAD(watch_events_waitq); + +static void xs_suspend_enter(void) +{ + spin_lock(&xs_state_lock); + xs_suspend_active++; + spin_unlock(&xs_state_lock); + wait_event(xs_state_exit_wq, xs_state_users == 0); +} + +static void xs_suspend_exit(void) +{ + xb_dev_generation_id++; + spin_lock(&xs_state_lock); + xs_suspend_active--; + spin_unlock(&xs_state_lock); + wake_up_all(&xs_state_enter_wq); +} + +static uint32_t xs_request_enter(struct xb_req_data *req) +{ + uint32_t rq_id; + + req->type = req->msg.type; + + spin_lock(&xs_state_lock); + + while (!xs_state_users && xs_suspend_active) { + spin_unlock(&xs_state_lock); + wait_event(xs_state_enter_wq, xs_suspend_active == 0); + spin_lock(&xs_state_lock); + } + + if (req->type == XS_TRANSACTION_START && !req->user_req) + xs_state_users++; + xs_state_users++; + rq_id = xs_request_id++; + + spin_unlock(&xs_state_lock); + + return rq_id; +} + +void xs_request_exit(struct xb_req_data *req) +{ + spin_lock(&xs_state_lock); + xs_state_users--; + if ((req->type == XS_TRANSACTION_START && req->msg.type == XS_ERROR) || + (req->type == XS_TRANSACTION_END && !req->user_req && + !WARN_ON_ONCE(req->msg.type == XS_ERROR && + !strcmp(req->body, "ENOENT")))) + xs_state_users--; + spin_unlock(&xs_state_lock); + + if (xs_suspend_active && !xs_state_users) + wake_up(&xs_state_exit_wq); +} + +static int get_error(const char *errorstring) +{ + unsigned int i; + + for (i = 0; strcmp(errorstring, xsd_errors[i].errstring) != 0; i++) { + if (i == ARRAY_SIZE(xsd_errors) - 1) { + pr_warn("xen store gave: unknown error %s\n", + errorstring); + return EINVAL; + } + } + return xsd_errors[i].errnum; +} + +static bool xenbus_ok(void) +{ + switch (xen_store_domain_type) { + case XS_LOCAL: + switch (system_state) { + case SYSTEM_POWER_OFF: + case SYSTEM_RESTART: + case SYSTEM_HALT: + return false; + default: + break; + } + return true; + case XS_PV: + case XS_HVM: + /* FIXME: Could check that the remote domain is alive, + * but it is normally initial domain. */ + return true; + default: + break; + } + return false; +} + +static bool test_reply(struct xb_req_data *req) +{ + if (req->state == xb_req_state_got_reply || !xenbus_ok()) { + /* read req->state before all other fields */ + virt_rmb(); + return true; + } + + /* Make sure to reread req->state each time. */ + barrier(); + + return false; +} + +static void *read_reply(struct xb_req_data *req) +{ + do { + wait_event(req->wq, test_reply(req)); + + if (!xenbus_ok()) + /* + * If we are in the process of being shut-down there is + * no point of trying to contact XenBus - it is either + * killed (xenstored application) or the other domain + * has been killed or is unreachable. + */ + return ERR_PTR(-EIO); + if (req->err) + return ERR_PTR(req->err); + + } while (req->state != xb_req_state_got_reply); + + return req->body; +} + +static void xs_send(struct xb_req_data *req, struct xsd_sockmsg *msg) +{ + bool notify; + + req->msg = *msg; + req->err = 0; + req->state = xb_req_state_queued; + init_waitqueue_head(&req->wq); + + /* Save the caller req_id and restore it later in the reply */ + req->caller_req_id = req->msg.req_id; + req->msg.req_id = xs_request_enter(req); + + mutex_lock(&xb_write_mutex); + list_add_tail(&req->list, &xb_write_list); + notify = list_is_singular(&xb_write_list); + mutex_unlock(&xb_write_mutex); + + if (notify) + wake_up(&xb_waitq); +} + +static void *xs_wait_for_reply(struct xb_req_data *req, struct xsd_sockmsg *msg) +{ + void *ret; + + ret = read_reply(req); + + xs_request_exit(req); + + msg->type = req->msg.type; + msg->len = req->msg.len; + + mutex_lock(&xb_write_mutex); + if (req->state == xb_req_state_queued || + req->state == xb_req_state_wait_reply) + req->state = xb_req_state_aborted; + else + kfree(req); + mutex_unlock(&xb_write_mutex); + + return ret; +} + +static void xs_wake_up(struct xb_req_data *req) +{ + wake_up(&req->wq); +} + +int xenbus_dev_request_and_reply(struct xsd_sockmsg *msg, void *par) +{ + struct xb_req_data *req; + struct kvec *vec; + + req = kmalloc(sizeof(*req) + sizeof(*vec), GFP_KERNEL); + if (!req) + return -ENOMEM; + + vec = (struct kvec *)(req + 1); + vec->iov_len = msg->len; + vec->iov_base = msg + 1; + + req->vec = vec; + req->num_vecs = 1; + req->cb = xenbus_dev_queue_reply; + req->par = par; + req->user_req = true; + + xs_send(req, msg); + + return 0; +} +EXPORT_SYMBOL(xenbus_dev_request_and_reply); + +/* Send message to xs, get kmalloc'ed reply. ERR_PTR() on error. */ +static void *xs_talkv(struct xenbus_transaction t, + enum xsd_sockmsg_type type, + const struct kvec *iovec, + unsigned int num_vecs, + unsigned int *len) +{ + struct xb_req_data *req; + struct xsd_sockmsg msg; + void *ret = NULL; + unsigned int i; + int err; + + req = kmalloc(sizeof(*req), GFP_NOIO | __GFP_HIGH); + if (!req) + return ERR_PTR(-ENOMEM); + + req->vec = iovec; + req->num_vecs = num_vecs; + req->cb = xs_wake_up; + req->user_req = false; + + msg.req_id = 0; + msg.tx_id = t.id; + msg.type = type; + msg.len = 0; + for (i = 0; i < num_vecs; i++) + msg.len += iovec[i].iov_len; + + xs_send(req, &msg); + + ret = xs_wait_for_reply(req, &msg); + if (len) + *len = msg.len; + + if (IS_ERR(ret)) + return ret; + + if (msg.type == XS_ERROR) { + err = get_error(ret); + kfree(ret); + return ERR_PTR(-err); + } + + if (msg.type != type) { + pr_warn_ratelimited("unexpected type [%d], expected [%d]\n", + msg.type, type); + kfree(ret); + return ERR_PTR(-EINVAL); + } + return ret; +} + +/* Simplified version of xs_talkv: single message. */ +static void *xs_single(struct xenbus_transaction t, + enum xsd_sockmsg_type type, + const char *string, + unsigned int *len) +{ + struct kvec iovec; + + iovec.iov_base = (void *)string; + iovec.iov_len = strlen(string) + 1; + return xs_talkv(t, type, &iovec, 1, len); +} + +/* Many commands only need an ack, don't care what it says. */ +static int xs_error(char *reply) +{ + if (IS_ERR(reply)) + return PTR_ERR(reply); + kfree(reply); + return 0; +} + +static unsigned int count_strings(const char *strings, unsigned int len) +{ + unsigned int num; + const char *p; + + for (p = strings, num = 0; p < strings + len; p += strlen(p) + 1) + num++; + + return num; +} + +/* Return the path to dir with /name appended. Buffer must be kfree()'ed. */ +static char *join(const char *dir, const char *name) +{ + char *buffer; + + if (strlen(name) == 0) + buffer = kasprintf(GFP_NOIO | __GFP_HIGH, "%s", dir); + else + buffer = kasprintf(GFP_NOIO | __GFP_HIGH, "%s/%s", dir, name); + return (!buffer) ? ERR_PTR(-ENOMEM) : buffer; +} + +static char **split(char *strings, unsigned int len, unsigned int *num) +{ + char *p, **ret; + + /* Count the strings. */ + *num = count_strings(strings, len); + + /* Transfer to one big alloc for easy freeing. */ + ret = kmalloc(*num * sizeof(char *) + len, GFP_NOIO | __GFP_HIGH); + if (!ret) { + kfree(strings); + return ERR_PTR(-ENOMEM); + } + memcpy(&ret[*num], strings, len); + kfree(strings); + + strings = (char *)&ret[*num]; + for (p = strings, *num = 0; p < strings + len; p += strlen(p) + 1) + ret[(*num)++] = p; + + return ret; +} + +char **xenbus_directory(struct xenbus_transaction t, + const char *dir, const char *node, unsigned int *num) +{ + char *strings, *path; + unsigned int len; + + path = join(dir, node); + if (IS_ERR(path)) + return (char **)path; + + strings = xs_single(t, XS_DIRECTORY, path, &len); + kfree(path); + if (IS_ERR(strings)) + return (char **)strings; + + return split(strings, len, num); +} +EXPORT_SYMBOL_GPL(xenbus_directory); + +/* Check if a path exists. Return 1 if it does. */ +int xenbus_exists(struct xenbus_transaction t, + const char *dir, const char *node) +{ + char **d; + int dir_n; + + d = xenbus_directory(t, dir, node, &dir_n); + if (IS_ERR(d)) + return 0; + kfree(d); + return 1; +} +EXPORT_SYMBOL_GPL(xenbus_exists); + +/* Get the value of a single file. + * Returns a kmalloced value: call free() on it after use. + * len indicates length in bytes. + */ +void *xenbus_read(struct xenbus_transaction t, + const char *dir, const char *node, unsigned int *len) +{ + char *path; + void *ret; + + path = join(dir, node); + if (IS_ERR(path)) + return (void *)path; + + ret = xs_single(t, XS_READ, path, len); + kfree(path); + return ret; +} +EXPORT_SYMBOL_GPL(xenbus_read); + +/* Write the value of a single file. + * Returns -err on failure. + */ +int xenbus_write(struct xenbus_transaction t, + const char *dir, const char *node, const char *string) +{ + const char *path; + struct kvec iovec[2]; + int ret; + + path = join(dir, node); + if (IS_ERR(path)) + return PTR_ERR(path); + + iovec[0].iov_base = (void *)path; + iovec[0].iov_len = strlen(path) + 1; + iovec[1].iov_base = (void *)string; + iovec[1].iov_len = strlen(string); + + ret = xs_error(xs_talkv(t, XS_WRITE, iovec, ARRAY_SIZE(iovec), NULL)); + kfree(path); + return ret; +} +EXPORT_SYMBOL_GPL(xenbus_write); + +/* Create a new directory. */ +int xenbus_mkdir(struct xenbus_transaction t, + const char *dir, const char *node) +{ + char *path; + int ret; + + path = join(dir, node); + if (IS_ERR(path)) + return PTR_ERR(path); + + ret = xs_error(xs_single(t, XS_MKDIR, path, NULL)); + kfree(path); + return ret; +} +EXPORT_SYMBOL_GPL(xenbus_mkdir); + +/* Destroy a file or directory (directories must be empty). */ +int xenbus_rm(struct xenbus_transaction t, const char *dir, const char *node) +{ + char *path; + int ret; + + path = join(dir, node); + if (IS_ERR(path)) + return PTR_ERR(path); + + ret = xs_error(xs_single(t, XS_RM, path, NULL)); + kfree(path); + return ret; +} +EXPORT_SYMBOL_GPL(xenbus_rm); + +/* Start a transaction: changes by others will not be seen during this + * transaction, and changes will not be visible to others until end. + */ +int xenbus_transaction_start(struct xenbus_transaction *t) +{ + char *id_str; + + id_str = xs_single(XBT_NIL, XS_TRANSACTION_START, "", NULL); + if (IS_ERR(id_str)) + return PTR_ERR(id_str); + + t->id = simple_strtoul(id_str, NULL, 0); + kfree(id_str); + return 0; +} +EXPORT_SYMBOL_GPL(xenbus_transaction_start); + +/* End a transaction. + * If abandon is true, transaction is discarded instead of committed. + */ +int xenbus_transaction_end(struct xenbus_transaction t, int abort) +{ + char abortstr[2]; + + if (abort) + strcpy(abortstr, "F"); + else + strcpy(abortstr, "T"); + + return xs_error(xs_single(t, XS_TRANSACTION_END, abortstr, NULL)); +} +EXPORT_SYMBOL_GPL(xenbus_transaction_end); + +/* Single read and scanf: returns -errno or num scanned. */ +int xenbus_scanf(struct xenbus_transaction t, + const char *dir, const char *node, const char *fmt, ...) +{ + va_list ap; + int ret; + char *val; + + val = xenbus_read(t, dir, node, NULL); + if (IS_ERR(val)) + return PTR_ERR(val); + + va_start(ap, fmt); + ret = vsscanf(val, fmt, ap); + va_end(ap); + kfree(val); + /* Distinctive errno. */ + if (ret == 0) + return -ERANGE; + return ret; +} +EXPORT_SYMBOL_GPL(xenbus_scanf); + +/* Read an (optional) unsigned value. */ +unsigned int xenbus_read_unsigned(const char *dir, const char *node, + unsigned int default_val) +{ + unsigned int val; + int ret; + + ret = xenbus_scanf(XBT_NIL, dir, node, "%u", &val); + if (ret <= 0) + val = default_val; + + return val; +} +EXPORT_SYMBOL_GPL(xenbus_read_unsigned); + +/* Single printf and write: returns -errno or 0. */ +int xenbus_printf(struct xenbus_transaction t, + const char *dir, const char *node, const char *fmt, ...) +{ + va_list ap; + int ret; + char *buf; + + va_start(ap, fmt); + buf = kvasprintf(GFP_NOIO | __GFP_HIGH, fmt, ap); + va_end(ap); + + if (!buf) + return -ENOMEM; + + ret = xenbus_write(t, dir, node, buf); + + kfree(buf); + + return ret; +} +EXPORT_SYMBOL_GPL(xenbus_printf); + +/* Takes tuples of names, scanf-style args, and void **, NULL terminated. */ +int xenbus_gather(struct xenbus_transaction t, const char *dir, ...) +{ + va_list ap; + const char *name; + int ret = 0; + + va_start(ap, dir); + while (ret == 0 && (name = va_arg(ap, char *)) != NULL) { + const char *fmt = va_arg(ap, char *); + void *result = va_arg(ap, void *); + char *p; + + p = xenbus_read(t, dir, name, NULL); + if (IS_ERR(p)) { + ret = PTR_ERR(p); + break; + } + if (fmt) { + if (sscanf(p, fmt, result) == 0) + ret = -EINVAL; + kfree(p); + } else + *(char **)result = p; + } + va_end(ap); + return ret; +} +EXPORT_SYMBOL_GPL(xenbus_gather); + +static int xs_watch(const char *path, const char *token) +{ + struct kvec iov[2]; + + iov[0].iov_base = (void *)path; + iov[0].iov_len = strlen(path) + 1; + iov[1].iov_base = (void *)token; + iov[1].iov_len = strlen(token) + 1; + + return xs_error(xs_talkv(XBT_NIL, XS_WATCH, iov, + ARRAY_SIZE(iov), NULL)); +} + +static int xs_unwatch(const char *path, const char *token) +{ + struct kvec iov[2]; + + iov[0].iov_base = (char *)path; + iov[0].iov_len = strlen(path) + 1; + iov[1].iov_base = (char *)token; + iov[1].iov_len = strlen(token) + 1; + + return xs_error(xs_talkv(XBT_NIL, XS_UNWATCH, iov, + ARRAY_SIZE(iov), NULL)); +} + +static struct xenbus_watch *find_watch(const char *token) +{ + struct xenbus_watch *i, *cmp; + + cmp = (void *)simple_strtoul(token, NULL, 16); + + list_for_each_entry(i, &watches, list) + if (i == cmp) + return i; + + return NULL; +} + +int xs_watch_msg(struct xs_watch_event *event) +{ + if (count_strings(event->body, event->len) != 2) { + kfree(event); + return -EINVAL; + } + event->path = (const char *)event->body; + event->token = (const char *)strchr(event->body, '\0') + 1; + + spin_lock(&watches_lock); + event->handle = find_watch(event->token); + if (event->handle != NULL && + (!event->handle->will_handle || + event->handle->will_handle(event->handle, + event->path, event->token))) { + spin_lock(&watch_events_lock); + list_add_tail(&event->list, &watch_events); + event->handle->nr_pending++; + wake_up(&watch_events_waitq); + spin_unlock(&watch_events_lock); + } else + kfree(event); + spin_unlock(&watches_lock); + + return 0; +} + +/* + * Certain older XenBus toolstack cannot handle reading values that are + * not populated. Some Xen 3.4 installation are incapable of doing this + * so if we are running on anything older than 4 do not attempt to read + * control/platform-feature-xs_reset_watches. + */ +static bool xen_strict_xenbus_quirk(void) +{ +#ifdef CONFIG_X86 + uint32_t eax, ebx, ecx, edx, base; + + base = xen_cpuid_base(); + cpuid(base + 1, &eax, &ebx, &ecx, &edx); + + if ((eax >> 16) < 4) + return true; +#endif + return false; + +} +static void xs_reset_watches(void) +{ + int err; + + if (!xen_hvm_domain() || xen_initial_domain()) + return; + + if (xen_strict_xenbus_quirk()) + return; + + if (!xenbus_read_unsigned("control", + "platform-feature-xs_reset_watches", 0)) + return; + + err = xs_error(xs_single(XBT_NIL, XS_RESET_WATCHES, "", NULL)); + if (err && err != -EEXIST) + pr_warn("xs_reset_watches failed: %d\n", err); +} + +/* Register callback to watch this node. */ +int register_xenbus_watch(struct xenbus_watch *watch) +{ + /* Pointer in ascii is the token. */ + char token[sizeof(watch) * 2 + 1]; + int err; + + sprintf(token, "%lX", (long)watch); + + watch->nr_pending = 0; + + down_read(&xs_watch_rwsem); + + spin_lock(&watches_lock); + BUG_ON(find_watch(token)); + list_add(&watch->list, &watches); + spin_unlock(&watches_lock); + + err = xs_watch(watch->node, token); + + if (err) { + spin_lock(&watches_lock); + list_del(&watch->list); + spin_unlock(&watches_lock); + } + + up_read(&xs_watch_rwsem); + + return err; +} +EXPORT_SYMBOL_GPL(register_xenbus_watch); + +void unregister_xenbus_watch(struct xenbus_watch *watch) +{ + struct xs_watch_event *event, *tmp; + char token[sizeof(watch) * 2 + 1]; + int err; + + sprintf(token, "%lX", (long)watch); + + down_read(&xs_watch_rwsem); + + spin_lock(&watches_lock); + BUG_ON(!find_watch(token)); + list_del(&watch->list); + spin_unlock(&watches_lock); + + err = xs_unwatch(watch->node, token); + if (err) + pr_warn("Failed to release watch %s: %i\n", watch->node, err); + + up_read(&xs_watch_rwsem); + + /* Make sure there are no callbacks running currently (unless + its us) */ + if (current->pid != xenwatch_pid) + mutex_lock(&xenwatch_mutex); + + /* Cancel pending watch events. */ + spin_lock(&watch_events_lock); + if (watch->nr_pending) { + list_for_each_entry_safe(event, tmp, &watch_events, list) { + if (event->handle != watch) + continue; + list_del(&event->list); + kfree(event); + } + watch->nr_pending = 0; + } + spin_unlock(&watch_events_lock); + + if (current->pid != xenwatch_pid) + mutex_unlock(&xenwatch_mutex); +} +EXPORT_SYMBOL_GPL(unregister_xenbus_watch); + +void xs_suspend(void) +{ + xs_suspend_enter(); + + down_write(&xs_watch_rwsem); + mutex_lock(&xs_response_mutex); +} + +void xs_resume(void) +{ + struct xenbus_watch *watch; + char token[sizeof(watch) * 2 + 1]; + + xb_init_comms(); + + mutex_unlock(&xs_response_mutex); + + xs_suspend_exit(); + + /* No need for watches_lock: the xs_watch_rwsem is sufficient. */ + list_for_each_entry(watch, &watches, list) { + sprintf(token, "%lX", (long)watch); + xs_watch(watch->node, token); + } + + up_write(&xs_watch_rwsem); +} + +void xs_suspend_cancel(void) +{ + mutex_unlock(&xs_response_mutex); + up_write(&xs_watch_rwsem); + + xs_suspend_exit(); +} + +static int xenwatch_thread(void *unused) +{ + struct xs_watch_event *event; + + xenwatch_pid = current->pid; + + for (;;) { + wait_event_interruptible(watch_events_waitq, + !list_empty(&watch_events)); + + if (kthread_should_stop()) + break; + + mutex_lock(&xenwatch_mutex); + + spin_lock(&watch_events_lock); + event = list_first_entry_or_null(&watch_events, + struct xs_watch_event, list); + if (event) { + list_del(&event->list); + event->handle->nr_pending--; + } + spin_unlock(&watch_events_lock); + + if (event) { + event->handle->callback(event->handle, event->path, + event->token); + kfree(event); + } + + mutex_unlock(&xenwatch_mutex); + } + + return 0; +} + +/* + * Wake up all threads waiting for a xenstore reply. In case of shutdown all + * pending replies will be marked as "aborted" in order to let the waiters + * return in spite of xenstore possibly no longer being able to reply. This + * will avoid blocking shutdown by a thread waiting for xenstore but being + * necessary for shutdown processing to proceed. + */ +static int xs_reboot_notify(struct notifier_block *nb, + unsigned long code, void *unused) +{ + struct xb_req_data *req; + + mutex_lock(&xb_write_mutex); + list_for_each_entry(req, &xs_reply_list, list) + wake_up(&req->wq); + list_for_each_entry(req, &xb_write_list, list) + wake_up(&req->wq); + mutex_unlock(&xb_write_mutex); + return NOTIFY_DONE; +} + +static struct notifier_block xs_reboot_nb = { + .notifier_call = xs_reboot_notify, +}; + +int xs_init(void) +{ + int err; + struct task_struct *task; + + register_reboot_notifier(&xs_reboot_nb); + + /* Initialize the shared memory rings to talk to xenstored */ + err = xb_init_comms(); + if (err) + return err; + + task = kthread_run(xenwatch_thread, NULL, "xenwatch"); + if (IS_ERR(task)) + return PTR_ERR(task); + + /* shutdown watches for kexec boot */ + xs_reset_watches(); + + return 0; +} |