/*
 * The owner field of the rw_semaphore structure will be set to
 * RWSEM_READ_OWNED when a reader grabs the lock. A writer will clear
 * the owner field when it unlocks. A reader, on the other hand, will
 * not touch the owner field when it unlocks.
 *
 * In essence, the owner field now has the following 3 states:
 *  1) 0
 *     - lock is free or the owner hasn't set the field yet
 *  2) RWSEM_READER_OWNED
 *     - lock is currently or previously owned by readers (lock is free
 *       or not set by owner yet)
 *  3) Other non-zero value
 *     - a writer owns the lock
 */
#define RWSEM_READER_OWNED	((struct task_struct *)1UL)

#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
/*
 * All writes to owner are protected by WRITE_ONCE() to make sure that
 * store tearing can't happen as optimistic spinners may read and use
 * the owner value concurrently without lock. Read from owner, however,
 * may not need READ_ONCE() as long as the pointer value is only used
 * for comparison and isn't being dereferenced.
 */
static inline void rwsem_set_owner(struct rw_semaphore *sem)
{
	WRITE_ONCE(sem->owner, current);
}

static inline void rwsem_clear_owner(struct rw_semaphore *sem)
{
	WRITE_ONCE(sem->owner, NULL);
}

static inline void rwsem_set_reader_owned(struct rw_semaphore *sem)
{
	/*
	 * We check the owner value first to make sure that we will only
	 * do a write to the rwsem cacheline when it is really necessary
	 * to minimize cacheline contention.
	 */
	if (sem->owner != RWSEM_READER_OWNED)
		WRITE_ONCE(sem->owner, RWSEM_READER_OWNED);
}

static inline bool rwsem_owner_is_writer(struct task_struct *owner)
{
	return owner && owner != RWSEM_READER_OWNED;
}

static inline bool rwsem_owner_is_reader(struct task_struct *owner)
{
	return owner == RWSEM_READER_OWNED;
}
#else
static inline void rwsem_set_owner(struct rw_semaphore *sem)
{
}

static inline void rwsem_clear_owner(struct rw_semaphore *sem)
{
}

static inline void rwsem_set_reader_owned(struct rw_semaphore *sem)
{
}
#endif
/cgit.cgi/linux/net-next.git/diff/net/switchdev/Kconfig?id=62ed8ceda1699acae01b666497f004bfd3d67a6f'>diff</a></td><td class='form'><form class='right' method='get' action='/cgit.cgi/linux/net-next.git/log/net/switchdev/Kconfig'>
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<div class='path'>path: <a href='/cgit.cgi/linux/net-next.git/commit/?id=62ed8ceda1699acae01b666497f004bfd3d67a6f'>root</a>/<a href='/cgit.cgi/linux/net-next.git/commit/net?id=62ed8ceda1699acae01b666497f004bfd3d67a6f'>net</a>/<a href='/cgit.cgi/linux/net-next.git/commit/net/switchdev?id=62ed8ceda1699acae01b666497f004bfd3d67a6f'>switchdev</a>/<a href='/cgit.cgi/linux/net-next.git/commit/net/switchdev/Kconfig?id=62ed8ceda1699acae01b666497f004bfd3d67a6f'>Kconfig</a></div><div class='content'><div class='cgit-panel'><b>diff options</b><form method='get'><input type='hidden' name='id' value='62ed8ceda1699acae01b666497f004bfd3d67a6f'/><table><tr><td colspan='2'/></tr><tr><td class='label'>context:</td><td class='ctrl'><select name='context' onchange='this.form.submit();'><option value='1'>1</option><option value='2'>2</option><option value='3' selected='selected'>3</option><option 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>Dmitry Torokhov &lt;dmitry.torokhov@gmail.com&gt;</td><td class='right'>2017-01-24 09:57:18 -0800</td></tr>
<tr><th>committer</th><td>Dmitry Torokhov &lt;dmitry.torokhov@gmail.com&gt;</td><td class='right'>2017-01-24 09:57:18 -0800</td></tr>
<tr><th>commit</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/net/switchdev/Kconfig?id=62ed8ceda1699acae01b666497f004bfd3d67a6f'>62ed8ceda1699acae01b666497f004bfd3d67a6f</a> (<a href='/cgit.cgi/linux/net-next.git/patch/net/switchdev/Kconfig?id=62ed8ceda1699acae01b666497f004bfd3d67a6f'>patch</a>)</td></tr>
<tr><th>tree</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/tree/?id=62ed8ceda1699acae01b666497f004bfd3d67a6f'>fe38c83c49dfd568b540666948ef78cb9d082c38</a> /<a href='/cgit.cgi/linux/net-next.git/tree/net/switchdev/Kconfig?id=62ed8ceda1699acae01b666497f004bfd3d67a6f'>net/switchdev/Kconfig</a></td></tr>
<tr><th>parent</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/net/switchdev/Kconfig?id=1c3415a06b1016a596bfe59e0cfee56c773aa958'>1c3415a06b1016a596bfe59e0cfee56c773aa958</a> (<a href='/cgit.cgi/linux/net-next.git/diff/net/switchdev/Kconfig?id=62ed8ceda1699acae01b666497f004bfd3d67a6f&amp;id2=1c3415a06b1016a596bfe59e0cfee56c773aa958'>diff</a>)</td></tr><tr><th>parent</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/net/switchdev/Kconfig?id=7a308bb3016f57e5be11a677d15b821536419d36'>7a308bb3016f57e5be11a677d15b821536419d36</a> (<a href='/cgit.cgi/linux/net-next.git/diff/net/switchdev/Kconfig?id=62ed8ceda1699acae01b666497f004bfd3d67a6f&amp;id2=7a308bb3016f57e5be11a677d15b821536419d36'>diff</a>)</td></tr></table>
<div class='commit-subject'>Merge tag 'v4.10-rc5' into for-linus</div><div class='commit-msg'>Sync up with mainline to apply fixup to a commit that came through
power supply tree.
</div><div class='diffstat-header'><a href='/cgit.cgi/linux/net-next.git/diff/?id=62ed8ceda1699acae01b666497f004bfd3d67a6f'>Diffstat</a> (limited to 'net/switchdev/Kconfig')</div><table summary='diffstat' class='diffstat'>