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![Takashi Iwai](/assets/img/avatar_default.png)
Currently the call of kill_fasync() from an interrupt handler might lead to potential spin deadlocks, as spotted by syzkaller. Unfortunately, it's not so trivial to fix this lock chain as it's involved with the tasklist_lock that is touched in allover places. As a temporary workaround, this patch provides the way to defer the async signal notification in a work. The new helper functions, snd_fasync_helper() and snd_kill_faync() are replacements for fasync_helper() and kill_fasync(), respectively. In addition, snd_fasync_free() needs to be called at the destructor of the relevant file object. Link: https://lore.kernel.org/r/20220728125945.29533-2-tiwai@suse.de Signed-off-by: Takashi Iwai <tiwai@suse.de>
241 lines
5.8 KiB
C
241 lines
5.8 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Misc and compatibility things
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* Copyright (c) by Jaroslav Kysela <perex@perex.cz>
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*/
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#include <linux/init.h>
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#include <linux/export.h>
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#include <linux/moduleparam.h>
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#include <linux/time.h>
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#include <linux/slab.h>
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#include <linux/ioport.h>
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#include <linux/fs.h>
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#include <sound/core.h>
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#ifdef CONFIG_SND_DEBUG
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#ifdef CONFIG_SND_DEBUG_VERBOSE
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#define DEFAULT_DEBUG_LEVEL 2
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#else
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#define DEFAULT_DEBUG_LEVEL 1
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#endif
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static int debug = DEFAULT_DEBUG_LEVEL;
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module_param(debug, int, 0644);
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MODULE_PARM_DESC(debug, "Debug level (0 = disable)");
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#endif /* CONFIG_SND_DEBUG */
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void release_and_free_resource(struct resource *res)
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{
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if (res) {
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release_resource(res);
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kfree(res);
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}
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}
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EXPORT_SYMBOL(release_and_free_resource);
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#ifdef CONFIG_SND_VERBOSE_PRINTK
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/* strip the leading path if the given path is absolute */
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static const char *sanity_file_name(const char *path)
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{
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if (*path == '/')
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return strrchr(path, '/') + 1;
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else
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return path;
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}
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#endif
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#if defined(CONFIG_SND_DEBUG) || defined(CONFIG_SND_VERBOSE_PRINTK)
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void __snd_printk(unsigned int level, const char *path, int line,
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const char *format, ...)
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{
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va_list args;
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#ifdef CONFIG_SND_VERBOSE_PRINTK
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int kern_level;
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struct va_format vaf;
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char verbose_fmt[] = KERN_DEFAULT "ALSA %s:%d %pV";
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bool level_found = false;
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#endif
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#ifdef CONFIG_SND_DEBUG
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if (debug < level)
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return;
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#endif
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va_start(args, format);
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#ifdef CONFIG_SND_VERBOSE_PRINTK
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vaf.fmt = format;
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vaf.va = &args;
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while ((kern_level = printk_get_level(vaf.fmt)) != 0) {
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const char *end_of_header = printk_skip_level(vaf.fmt);
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/* Ignore KERN_CONT. We print filename:line for each piece. */
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if (kern_level >= '0' && kern_level <= '7') {
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memcpy(verbose_fmt, vaf.fmt, end_of_header - vaf.fmt);
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level_found = true;
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}
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vaf.fmt = end_of_header;
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}
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if (!level_found && level)
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memcpy(verbose_fmt, KERN_DEBUG, sizeof(KERN_DEBUG) - 1);
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printk(verbose_fmt, sanity_file_name(path), line, &vaf);
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#else
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vprintk(format, args);
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#endif
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va_end(args);
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}
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EXPORT_SYMBOL_GPL(__snd_printk);
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#endif
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#ifdef CONFIG_PCI
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#include <linux/pci.h>
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/**
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* snd_pci_quirk_lookup_id - look up a PCI SSID quirk list
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* @vendor: PCI SSV id
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* @device: PCI SSD id
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* @list: quirk list, terminated by a null entry
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*
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* Look through the given quirk list and finds a matching entry
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* with the same PCI SSID. When subdevice is 0, all subdevice
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* values may match.
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*
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* Returns the matched entry pointer, or NULL if nothing matched.
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*/
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const struct snd_pci_quirk *
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snd_pci_quirk_lookup_id(u16 vendor, u16 device,
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const struct snd_pci_quirk *list)
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{
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const struct snd_pci_quirk *q;
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for (q = list; q->subvendor || q->subdevice; q++) {
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if (q->subvendor != vendor)
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continue;
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if (!q->subdevice ||
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(device & q->subdevice_mask) == q->subdevice)
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return q;
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}
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return NULL;
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}
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EXPORT_SYMBOL(snd_pci_quirk_lookup_id);
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/**
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* snd_pci_quirk_lookup - look up a PCI SSID quirk list
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* @pci: pci_dev handle
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* @list: quirk list, terminated by a null entry
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*
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* Look through the given quirk list and finds a matching entry
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* with the same PCI SSID. When subdevice is 0, all subdevice
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* values may match.
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*
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* Returns the matched entry pointer, or NULL if nothing matched.
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*/
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const struct snd_pci_quirk *
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snd_pci_quirk_lookup(struct pci_dev *pci, const struct snd_pci_quirk *list)
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{
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if (!pci)
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return NULL;
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return snd_pci_quirk_lookup_id(pci->subsystem_vendor,
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pci->subsystem_device,
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list);
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}
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EXPORT_SYMBOL(snd_pci_quirk_lookup);
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#endif
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/*
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* Deferred async signal helpers
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*
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* Below are a few helper functions to wrap the async signal handling
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* in the deferred work. The main purpose is to avoid the messy deadlock
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* around tasklist_lock and co at the kill_fasync() invocation.
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* fasync_helper() and kill_fasync() are replaced with snd_fasync_helper()
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* and snd_kill_fasync(), respectively. In addition, snd_fasync_free() has
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* to be called at releasing the relevant file object.
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*/
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struct snd_fasync {
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struct fasync_struct *fasync;
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int signal;
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int poll;
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int on;
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struct list_head list;
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};
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static DEFINE_SPINLOCK(snd_fasync_lock);
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static LIST_HEAD(snd_fasync_list);
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static void snd_fasync_work_fn(struct work_struct *work)
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{
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struct snd_fasync *fasync;
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spin_lock_irq(&snd_fasync_lock);
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while (!list_empty(&snd_fasync_list)) {
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fasync = list_first_entry(&snd_fasync_list, struct snd_fasync, list);
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list_del_init(&fasync->list);
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spin_unlock_irq(&snd_fasync_lock);
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if (fasync->on)
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kill_fasync(&fasync->fasync, fasync->signal, fasync->poll);
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spin_lock_irq(&snd_fasync_lock);
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}
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spin_unlock_irq(&snd_fasync_lock);
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}
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static DECLARE_WORK(snd_fasync_work, snd_fasync_work_fn);
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int snd_fasync_helper(int fd, struct file *file, int on,
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struct snd_fasync **fasyncp)
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{
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struct snd_fasync *fasync = NULL;
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if (on) {
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fasync = kzalloc(sizeof(*fasync), GFP_KERNEL);
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if (!fasync)
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return -ENOMEM;
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INIT_LIST_HEAD(&fasync->list);
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}
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spin_lock_irq(&snd_fasync_lock);
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if (*fasyncp) {
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kfree(fasync);
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fasync = *fasyncp;
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} else {
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if (!fasync) {
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spin_unlock_irq(&snd_fasync_lock);
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return 0;
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}
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*fasyncp = fasync;
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}
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fasync->on = on;
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spin_unlock_irq(&snd_fasync_lock);
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return fasync_helper(fd, file, on, &fasync->fasync);
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}
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EXPORT_SYMBOL_GPL(snd_fasync_helper);
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void snd_kill_fasync(struct snd_fasync *fasync, int signal, int poll)
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{
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unsigned long flags;
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if (!fasync || !fasync->on)
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return;
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spin_lock_irqsave(&snd_fasync_lock, flags);
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fasync->signal = signal;
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fasync->poll = poll;
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list_move(&fasync->list, &snd_fasync_list);
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schedule_work(&snd_fasync_work);
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spin_unlock_irqrestore(&snd_fasync_lock, flags);
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}
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EXPORT_SYMBOL_GPL(snd_kill_fasync);
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void snd_fasync_free(struct snd_fasync *fasync)
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{
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if (!fasync)
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return;
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fasync->on = 0;
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flush_work(&snd_fasync_work);
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kfree(fasync);
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}
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EXPORT_SYMBOL_GPL(snd_fasync_free);
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