freebsd-dev/sys/compat/linuxkpi/common/include/linux/srcu.h
Hans Petter Selasky f3de9af633 Fix problem regarding priority inversion when using the concurrency
kit, CK, in the LinuxKPI.

When threads are pinned to a CPU core or when there is only one CPU,
it can happen that a higher priority thread can call the CK
synchronize function while a lower priority thread holds the read
lock. Because the CK's synchronize is a simple wait loop this can lead
to a deadlock situation. To solve this problem use the recently
introduced CK's wait callback function.

When detecting a CK blocking condition figure out the lowest priority
among the blockers and update the calling thread's priority and
yield. If another CPU core is holding the read lock, pin the thread to
the blocked CPU core and update the priority. The calling threads
priority and CPU bindings are restored before return.

If a thread holding a CK read lock is detected to be sleeping, pause()
will be used instead of yield().

MFC after:		1 week
Sponsored by:		Mellanox Technologies
2017-04-19 13:03:29 +00:00

47 lines
1.8 KiB
C

/*-
* Copyright (c) 2015-2017 Mellanox Technologies, Ltd.
* All rights reserved.
*
* 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 _LINUX_SRCU_H_
#define _LINUX_SRCU_H_
struct srcu_struct {
};
#define srcu_dereference(ptr,srcu) ((__typeof(*(ptr)) *)(ptr))
/* prototypes */
extern int srcu_read_lock(struct srcu_struct *);
extern void srcu_read_unlock(struct srcu_struct *, int index);
extern void synchronize_srcu(struct srcu_struct *);
extern void srcu_barrier(struct srcu_struct *);
extern int init_srcu_struct(struct srcu_struct *);
extern void cleanup_srcu_struct(struct srcu_struct *);
#endif /* _LINUX_SRCU_H_ */