/* * 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 <mchehab@s-opensource.com></td><td class='right'>2016-12-26 14:09:28 -0200</td></tr> <tr><th>committer</th><td>Mauro Carvalho Chehab <mchehab@s-opensource.com></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&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&id=0e0694ff1a7791274946b7f51bae692da0001a08'>53d28f58d793c151aa870f17d38ddec6ac01ec7a</a> /<a href='/cgit.cgi/linux/net-next.git/tree/sound/usb/usx2y/usX2Yhwdep.c?h=nds-private-remove&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&id=65390ea01ce678379da32b01f39fcfac4903f256'>65390ea01ce678379da32b01f39fcfac4903f256</a> (<a href='/cgit.cgi/linux/net-next.git/diff/sound/usb/usx2y/usX2Yhwdep.c?h=nds-private-remove&id=0e0694ff1a7791274946b7f51bae692da0001a08&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&id=c739c0a7c3c2472d7562b8f802cdce44d2597c8b'>c739c0a7c3c2472d7562b8f802cdce44d2597c8b</a> (<a href='/cgit.cgi/linux/net-next.git/diff/sound/usb/usx2y/usX2Yhwdep.c?h=nds-private-remove&id=0e0694ff1a7791274946b7f51bae692da0001a08&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 < 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&id=0e0694ff1a7791274946b7f51bae692da0001a08'>Diffstat</a> (limited to 'sound/usb/usx2y/usX2Yhwdep.c')</div><table summary='diffstat' class='diffstat'>