/*-
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
* Copyright (c) 2019, 2020 Jeffrey Roberson <jeff@FreeBSD.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice unmodified, this list of conditions, and the following
* disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* $FreeBSD$
*/
#ifndef _SYS_SMR_TYPES_H_
#define _SYS_SMR_TYPES_H_
#include <sys/_smr.h>
/*
* SMR Accessors are meant to provide safe access to SMR protected
* pointers and prevent misuse and accidental access.
*
* Accessors are grouped by type:
* entered - Use while in a read section (between smr_enter/smr_exit())
* serialized - Use while holding a lock that serializes writers. Updates
* are synchronized with readers via included barriers.
* unserialized - Use after the memory is out of scope and not visible to
* readers.
*
* All acceses include a parameter for an assert to verify the required
* synchronization. For example, a writer might use:
*
* smr_serialized_store(pointer, value, mtx_owned(&writelock));
*
* These are only enabled in INVARIANTS kernels.
*/
/* Type restricting pointer access to force smr accessors. */
#define SMR_POINTER(type) \
struct { \
type __ptr; /* Do not access directly */ \
}
/*
* Read from an SMR protected pointer while in a read section.
*/
#define smr_entered_load(p, smr) ({ \
SMR_ASSERT(SMR_ENTERED((smr)), "smr_entered_load"); \
(__typeof((p)->__ptr))atomic_load_acq_ptr((uintptr_t *)&(p)->__ptr); \
})
/*
* Read from an SMR protected pointer while serialized by an
* external mechanism. 'ex' should contain an assert that the
* external mechanism is held. i.e. mtx_owned()
*/
#define smr_serialized_load(p, ex) ({ \
SMR_ASSERT(ex, "smr_serialized_load"); \
(__typeof((p)->__ptr))atomic_load_ptr(&(p)->__ptr); \
})
/*
* Store 'v' to an SMR protected pointer while serialized by an
* external mechanism. 'ex' should contain an assert that the
* external mechanism is held. i.e. mtx_owned()
*
* Writers that are serialized with mutual exclusion or on a single
* thread should use smr_serialized_store() rather than swap.
*/
#define smr_serialized_store(p, v, ex) do { \
SMR_ASSERT(ex, "smr_serialized_store"); \
__typeof((p)->__ptr) _v = (v); \
atomic_store_rel_ptr((uintptr_t *)&(p)->__ptr, (uintptr_t)_v); \
} while (0)
/*
* swap 'v' with an SMR protected pointer and return the old value
* while serialized by an external mechanism. 'ex' should contain
* an assert that the external mechanism is provided. i.e. mtx_owned()
*
* Swap permits multiple writers to update a pointer concurrently.
*/
#define smr_serialized_swap(p, v, ex) ({ \
SMR_ASSERT(ex, "smr_serialized_swap"); \
__typeof((p)->__ptr) _v = (v); \
/* Release barrier guarantees contents are visible to reader */ \
atomic_thread_fence_rel(); \
(__typeof((p)->__ptr))atomic_swap_ptr( \
(uintptr_t *)&(p)->__ptr, (uintptr_t)_v); \
})
/*
* Read from an SMR protected pointer when no serialization is required
* such as in the destructor callback or when the caller guarantees other
* synchronization.
*/
#define smr_unserialized_load(p, ex) ({ \
SMR_ASSERT(ex, "smr_unserialized_load"); \
(__typeof((p)->__ptr))atomic_load_ptr(&(p)->__ptr); \
})
/*
* Store to an SMR protected pointer when no serialiation is required
* such as in the destructor callback or when the caller guarantees other
* synchronization.
*/
#define smr_unserialized_store(p, v, ex) do { \
SMR_ASSERT(ex, "smr_unserialized_store"); \
__typeof((p)->__ptr) _v = (v); \
atomic_store_ptr((uintptr_t *)&(p)->__ptr, (uintptr_t)_v); \
} while (0)
#ifndef _KERNEL
/*
* Load an SMR protected pointer when accessing kernel data structures through
* libkvm.
*/
#define smr_kvm_load(p) ((p)->__ptr)
#endif /* !_KERNEL */
#endif /* !_SYS_SMR_TYPES_H_ */
