/* * Queue read/write lock * * 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 */ #ifndef __ASM_GENERIC_QRWLOCK_H #define __ASM_GENERIC_QRWLOCK_H #include #include #include #include /* * Writer states & reader shift and bias. * * | +0 | +1 | +2 | +3 | * ----+----+----+----+----+ * LE | 78 | 56 | 34 | 12 | 0x12345678 * ----+----+----+----+----+ * | wr | rd | * +----+----+----+----+ * * ----+----+----+----+----+ * BE | 12 | 34 | 56 | 78 | 0x12345678 * ----+----+----+----+----+ * | rd | wr | * +----+----+----+----+ */ #define _QW_WAITING 1 /* A writer is waiting */ #define _QW_LOCKED 0xff /* A writer holds the lock */ #define _QW_WMASK 0xff /* Writer mask */ #define _QR_SHIFT 8 /* Reader count shift */ #define _QR_BIAS (1U << _QR_SHIFT) /* * External function declarations */ extern void queued_read_lock_slowpath(struct qrwlock *lock, u32 cnts); extern void queued_write_lock_slowpath(struct qrwlock *lock); /** * queued_read_can_lock- would read_trylock() succeed? * @lock: Pointer to queue rwlock structure */ static inline int queued_read_can_lock(struct qrwlock *lock) { return !(atomic_read(&lock->cnts) & _QW_WMASK); } /** * queued_write_can_lock- would write_trylock() succeed? * @lock: Pointer to queue rwlock structure */ static inline int queued_write_can_lock(struct qrwlock *lock) { return !atomic_read(&lock->cnts); } /** * queued_read_trylock - try to acquire read lock of a queue rwlock * @lock : Pointer to queue rwlock structure * Return: 1 if lock acquired, 0 if failed */ static inline int queued_read_trylock(struct qrwlock *lock) { u32 cnts; cnts = atomic_read(&lock->cnts); if (likely(!(cnts & _QW_WMASK))) { cnts = (u32)atomic_add_return_acquire(_QR_BIAS, &lock->cnts); if (likely(!(cnts & _QW_WMASK))) return 1; atomic_sub(_QR_BIAS, &lock->cnts); } return 0; } /** * queued_write_trylock - try to acquire write lock of a queue rwlock * @lock : Pointer to queue rwlock structure * Return: 1 if lock acquired, 0 if failed */ static inline int queued_write_trylock(struct qrwlock *lock) { u32 cnts; cnts = atomic_read(&lock->cnts); if (unlikely(cnts)) return 0; return likely(atomic_cmpxchg_acquire(&lock->cnts, cnts, cnts | _QW_LOCKED) == cnts); } /** * queued_read_lock - acquire read lock of a queue rwlock * @lock: Pointer to queue rwlock structure */ static inline void queued_read_lock(struct qrwlock *lock) { u32 cnts; cnts = atomic_add_return_acquire(_QR_BIAS, &lock->cnts); if (likely(!(cnts & _QW_WMASK))) return; /* The slowpath will decrement the reader count, if necessary. */ queued_read_lock_slowpath(lock, cnts); } /** * queued_write_lock - acquire write lock of a queue rwlock * @lock : Pointer to queue rwlock structure */ static inline void queued_write_lock(struct qrwlock *lock) { /* Optimize for the unfair lock case where the fair flag is 0. */ if (atomic_cmpxchg_acquire(&lock->cnts, 0, _QW_LOCKED) == 0) return; queued_write_lock_slowpath(lock); } /** * queued_read_unlock - release read lock of a queue rwlock * @lock : Pointer to queue rwlock structure */ static inline void queued_read_unlock(struct qrwlock *lock) { /* * Atomically decrement the reader count */ (void)atomic_sub_return_release(_QR_BIAS, &lock->cnts); } /** * __qrwlock_write_byte - retrieve the write byte address of a queue rwlock * @lock : Pointer to queue rwlock structure * Return: the write byte address of a queue rwlock */ static inline u8 *__qrwlock_write_byte(struct qrwlock *lock) { return (u8 *)lock + 3 * IS_BUILTIN(CONFIG_CPU_BIG_ENDIAN); } /** * queued_write_unlock - release write lock of a queue rwlock * @lock : Pointer to queue rwlock structure */ static inline void queued_write_unlock(struct qrwlock *lock) { smp_store_release(__qrwlock_write_byte(lock), 0); } /* * Remapping rwlock architecture specific functions to the corresponding * queue rwlock functions. */ #define arch_read_can_lock(l) queued_read_can_lock(l) #define arch_write_can_lock(l) queued_write_can_lock(l) #define arch_read_lock(l) queued_read_lock(l) #define arch_write_lock(l) queued_write_lock(l) #define arch_read_trylock(l) queued_read_trylock(l) #define arch_write_trylock(l) queued_write_trylock(l) #define arch_read_unlock(l) queued_read_unlock(l) #define arch_write_unlock(l) queued_write_unlock(l) #endif /* __ASM_GENERIC_QRWLOCK_H */ 'right'>2017-01-31 10:59:48 +0100 commit433e19cf33d34bb6751c874a9c00980552fe508c (patch) treece6547ef2987fbb289fa28f03536328a42781651 /net/wimax/Kconfig parent191e885a2e130e639bb0c8ee350d7047294f2ce6 (diff)
Drivers: hv: vmbus: finally fix hv_need_to_signal_on_read()
Commit a389fcfd2cb5 ("Drivers: hv: vmbus: Fix signaling logic in hv_need_to_signal_on_read()") added the proper mb(), but removed the test "prev_write_sz < pending_sz" when making the signal decision. As a result, the guest can signal the host unnecessarily, and then the host can throttle the guest because the host thinks the guest is buggy or malicious; finally the user running stress test can perceive intermittent freeze of the guest. This patch brings back the test, and properly handles the in-place consumption APIs used by NetVSC (see get_next_pkt_raw(), put_pkt_raw() and commit_rd_index()). Fixes: a389fcfd2cb5 ("Drivers: hv: vmbus: Fix signaling logic in hv_need_to_signal_on_read()") Signed-off-by: Dexuan Cui <decui@microsoft.com> Reported-by: Rolf Neugebauer <rolf.neugebauer@docker.com> Tested-by: Rolf Neugebauer <rolf.neugebauer@docker.com> Cc: "K. Y. Srinivasan" <kys@microsoft.com> Cc: Haiyang Zhang <haiyangz@microsoft.com> Cc: Stephen Hemminger <sthemmin@microsoft.com> Cc: <stable@vger.kernel.org> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'net/wimax/Kconfig')