/* * 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 ommitdiff
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authorStanislaw Gruszka <sgruszka@redhat.com>2017-01-29 12:40:52 +0100
committerKalle Valo <kvalo@codeaurora.org>2017-01-31 09:08:52 +0200
commit33e962c8871f015f5c8978384553dddcf5b81b22 (patch)
tree43aff96c2ee21d9e0fa2018457778a4de52053cd /include/scsi/scsi_devinfo.h
parent575ddce0507789bf9830d089557d2199d2f91865 (diff)
rt2x00: fix clk_get call
clk_get() takes two arguments and might return ERR_PTR(), so we have to nullify pointer on that case, to do not break further call to clk_get_rate(). Reported-by: Felix Fietkau <nbd@nbd.name> Fixes: 34db70b92fae ("rt2x00: add copy of clk for soc devices") Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com> Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Diffstat (limited to 'include/scsi/scsi_devinfo.h')