/*
 * Queued read/write locks
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * (C) Copyright 2013-2014 Hewlett-Packard Development Company, L.P.
 *
 * Authors: Waiman Long <waiman.long@hp.com>
 */
#include <linux/smp.h>
#include <linux/bug.h>
#include <linux/cpumask.h>
#include <linux/percpu.h>
#include <linux/hardirq.h>
#include <asm/qrwlock.h>

/*
 * This internal data structure is used for optimizing access to some of
 * the subfields within the atomic_t cnts.
 */
struct __qrwlock {
	union {
		atomic_t cnts;
		struct {
#ifdef __LITTLE_ENDIAN
			u8 wmode;	/* Writer mode   */
			u8 rcnts[3];	/* Reader counts */
#else
			u8 rcnts[3];	/* Reader counts */
			u8 wmode;	/* Writer mode   */
#endif
		};
	};
	arch_spinlock_t	lock;
};

/**
 * rspin_until_writer_unlock - inc reader count & spin until writer is gone
 * @lock  : Pointer to queue rwlock structure
 * @writer: Current queue rwlock writer status byte
 *
 * In interrupt context or at the head of the queue, the reader will just
 * increment the reader count & wait until the writer releases the lock.
 */
static __always_inline void
rspin_until_writer_unlock(struct qrwlock *lock, u32 cnts)
{
	while ((cnts & _QW_WMASK) == _QW_LOCKED) {
		cpu_relax();
		cnts = atomic_read_acquire(&lock->cnts);
	}
}

/**
 * queued_read_lock_slowpath - acquire read lock of a queue rwlock
 * @lock: Pointer to queue rwlock structure
 * @cnts: Current qrwlock lock value
 */
void queued_read_lock_slowpath(struct qrwlock *lock, u32 cnts)
{
	/*
	 * Readers come here when they cannot get the lock without waiting
	 */
	if (unlikely(in_interrupt())) {
		/*
		 * Readers in interrupt context will get the lock immediately
		 * if the writer is just waiting (not holding the lock yet).
		 * The rspin_until_writer_unlock() function returns immediately
		 * in this case. Otherwise, they will spin (with ACQUIRE
		 * semantics) until the lock is available without waiting in
		 * the queue.
		 */
		rspin_until_writer_unlock(lock, cnts);
		return;
	}
	atomic_sub(_QR_BIAS, &lock->cnts);

	/*
	 * Put the reader into the wait queue
	 */
	arch_spin_lock(&lock->wait_lock);

	/*
	 * The ACQUIRE semantics of the following spinning code ensure
	 * that accesses can't leak upwards out of our subsequent critical
	 * section in the case that the lock is currently held for write.
	 */
	cnts = atomic_fetch_add_acquire(_QR_BIAS, &lock->cnts);
	rspin_until_writer_unlock(lock, cnts);

	/*
	 * Signal the next one in queue to become queue head
	 */
	arch_spin_unlock(&lock->wait_lock);
}
EXPORT_SYMBOL(queued_read_lock_slowpath);

/**
 * queued_write_lock_slowpath - acquire write lock of a queue rwlock
 * @lock : Pointer to queue rwlock structure
 */
void queued_write_lock_slowpath(struct qrwlock *lock)
{
	u32 cnts;

	/* Put the writer into the wait queue */
	arch_spin_lock(&lock->wait_lock);

	/* Try to acquire the lock directly if no reader is present */
	if (!atomic_read(&lock->cnts) &&
	    (atomic_cmpxchg_acquire(&lock->cnts, 0, _QW_LOCKED) == 0))
		goto unlock;

	/*
	 * Set the waiting flag to notify readers that a writer is pending,
	 * or wait for a previous writer to go away.
	 */
	for (;;) {
		struct __qrwlock *l = (struct __qrwlock *)lock;

		if (!READ_ONCE(l->wmode) &&
		   (cmpxchg_relaxed(&l->wmode, 0, _QW_WAITING) == 0))
			break;

		cpu_relax();
	}

	/* When no more readers, set the locked flag */
	for (;;) {
		cnts = atomic_read(&lock->cnts);
		if ((cnts == _QW_WAITING) &&
		    (atomic_cmpxchg_acquire(&lock->cnts, _QW_WAITING,
					    _QW_LOCKED) == _QW_WAITING))
			break;

		cpu_relax();
	}
unlock:
	arch_spin_unlock(&lock->wait_lock);
}
EXPORT_SYMBOL(queued_write_lock_slowpath);
tion value='4'>4</option><option value='5'>5</option><option value='6'>6</option><option value='7'>7</option><option value='8'>8</option><option value='9'>9</option><option value='10'>10</option><option value='15'>15</option><option value='20'>20</option><option value='25'>25</option><option value='30'>30</option><option value='35'>35</option><option value='40'>40</option></select></td></tr><tr><td class='label'>space:</td><td class='ctrl'><select name='ignorews' onchange='this.form.submit();'><option value='0' selected='selected'>include</option><option value='1'>ignore</option></select></td></tr><tr><td class='label'>mode:</td><td class='ctrl'><select name='dt' onchange='this.form.submit();'><option value='0' selected='selected'>unified</option><option value='1'>ssdiff</option><option value='2'>stat only</option></select></td></tr><tr><td/><td class='ctrl'><noscript><input type='submit' value='reload'/></noscript></td></tr></table></form></div><table summary='commit info' class='commit-info'>
<tr><th>author</th><td>Mauro Carvalho Chehab &lt;mchehab@s-opensource.com&gt;</td><td class='right'>2016-12-26 14:09:28 -0200</td></tr>
<tr><th>committer</th><td>Mauro Carvalho Chehab &lt;mchehab@s-opensource.com&gt;</td><td class='right'>2016-12-26 14:09:28 -0200</td></tr>
<tr><th>commit</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/sound/usb/usx2y/usX2Yhwdep.c?h=nds-private-remove&amp;id=0e0694ff1a7791274946b7f51bae692da0001a08'>0e0694ff1a7791274946b7f51bae692da0001a08</a> (<a href='/cgit.cgi/linux/net-next.git/patch/sound/usb/usx2y/usX2Yhwdep.c?id=0e0694ff1a7791274946b7f51bae692da0001a08'>patch</a>)</td></tr>
<tr><th>tree</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/tree/?h=nds-private-remove&amp;id=0e0694ff1a7791274946b7f51bae692da0001a08'>53d28f58d793c151aa870f17d38ddec6ac01ec7a</a> /<a href='/cgit.cgi/linux/net-next.git/tree/sound/usb/usx2y/usX2Yhwdep.c?h=nds-private-remove&amp;id=0e0694ff1a7791274946b7f51bae692da0001a08'>sound/usb/usx2y/usX2Yhwdep.c</a></td></tr>
<tr><th>parent</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/sound/usb/usx2y/usX2Yhwdep.c?h=nds-private-remove&amp;id=65390ea01ce678379da32b01f39fcfac4903f256'>65390ea01ce678379da32b01f39fcfac4903f256</a> (<a href='/cgit.cgi/linux/net-next.git/diff/sound/usb/usx2y/usX2Yhwdep.c?h=nds-private-remove&amp;id=0e0694ff1a7791274946b7f51bae692da0001a08&amp;id2=65390ea01ce678379da32b01f39fcfac4903f256'>diff</a>)</td></tr><tr><th>parent</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/sound/usb/usx2y/usX2Yhwdep.c?h=nds-private-remove&amp;id=c739c0a7c3c2472d7562b8f802cdce44d2597c8b'>c739c0a7c3c2472d7562b8f802cdce44d2597c8b</a> (<a href='/cgit.cgi/linux/net-next.git/diff/sound/usb/usx2y/usX2Yhwdep.c?h=nds-private-remove&amp;id=0e0694ff1a7791274946b7f51bae692da0001a08&amp;id2=c739c0a7c3c2472d7562b8f802cdce44d2597c8b'>diff</a>)</td></tr></table>
<div class='commit-subject'>Merge branch 'patchwork' into v4l_for_linus</div><div class='commit-msg'>* patchwork:
  [media] s5k4ecgx: select CRC32 helper
  [media] dvb: avoid warning in dvb_net
  [media] v4l: tvp5150: Don't override output pinmuxing at stream on/off time
  [media] v4l: tvp5150: Fix comment regarding output pin muxing
  [media] v4l: tvp5150: Reset device at probe time, not in get/set format handlers
  [media] pctv452e: move buffer to heap, no mutex
  [media] media/cobalt: use pci_irq_allocate_vectors
  [media] cec: fix race between configuring and unconfiguring
  [media] cec: move cec_report_phys_addr into cec_config_thread_func
  [media] cec: replace cec_report_features by cec_fill_msg_report_features
  [media] cec: update log_addr[] before finishing configuration
  [media] cec: CEC_MSG_GIVE_FEATURES should abort for CEC version &lt; 2
  [media] cec: when canceling a message, don't overwrite old status info
  [media] cec: fix report_current_latency
  [media] smiapp: Make suspend and resume functions __maybe_unused
  [media] smiapp: Implement power-on and power-off sequences without runtime PM
</div><div class='diffstat-header'><a href='/cgit.cgi/linux/net-next.git/diff/?h=nds-private-remove&amp;id=0e0694ff1a7791274946b7f51bae692da0001a08'>Diffstat</a> (limited to 'sound/usb/usx2y/usX2Yhwdep.c')</div><table summary='diffstat' class='diffstat'>