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cdbb997822
This is similar to NTSYNC_IOC_WAIT_ANY, but waits until all of the objects are simultaneously signaled, and then acquires all of them as a single atomic operation. Because acquisition of multiple objects is atomic, some complex locking is required. We cannot simply spin-lock multiple objects simultaneously, as that may disable preëmption for a problematically long time. Instead, modifying any object which may be involved in a wait-all operation takes a device-wide sleeping mutex, "wait_all_lock", instead of the normal object spinlock. Because wait-for-all is a rare operation, in order to optimize wait-for-any, this lock is only taken when necessary. "all_hint" is used to mark objects which are involved in a wait-for-all operation, and if an object is not, only its spinlock is taken. The locking scheme used here was written by Peter Zijlstra. Signed-off-by: Elizabeth Figura <zfigura@codeweavers.com> Link: https://lore.kernel.org/r/20241213193511.457338-5-zfigura@codeweavers.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
38 lines
800 B
C
38 lines
800 B
C
/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
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/*
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* Kernel support for NT synchronization primitive emulation
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*
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* Copyright (C) 2021-2022 Elizabeth Figura <zfigura@codeweavers.com>
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*/
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#ifndef __LINUX_NTSYNC_H
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#define __LINUX_NTSYNC_H
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#include <linux/types.h>
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struct ntsync_sem_args {
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__u32 count;
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__u32 max;
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};
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#define NTSYNC_WAIT_REALTIME 0x1
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struct ntsync_wait_args {
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__u64 timeout;
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__u64 objs;
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__u32 count;
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__u32 index;
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__u32 flags;
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__u32 pad[3];
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};
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#define NTSYNC_MAX_WAIT_COUNT 64
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#define NTSYNC_IOC_CREATE_SEM _IOW ('N', 0x80, struct ntsync_sem_args)
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#define NTSYNC_IOC_WAIT_ANY _IOWR('N', 0x82, struct ntsync_wait_args)
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#define NTSYNC_IOC_WAIT_ALL _IOWR('N', 0x83, struct ntsync_wait_args)
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#define NTSYNC_IOC_SEM_RELEASE _IOWR('N', 0x81, __u32)
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#endif
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