[PATCH] Add thinktime_spin parameter
[fio.git] / syslet.h
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1#ifndef _LINUX_SYSLET_H
2#define _LINUX_SYSLET_H
3/*
4 * The syslet subsystem - asynchronous syscall execution support.
5 *
6 * Started by Ingo Molnar:
7 *
8 * Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
9 *
10 * User-space API/ABI definitions:
11 */
12
13/*
14 * This is the 'Syslet Atom' - the basic unit of execution
15 * within the syslet framework. A syslet always represents
16 * a single system-call plus its arguments, plus has conditions
17 * attached to it that allows the construction of larger
18 * programs from these atoms. User-space variables can be used
19 * (for example a loop index) via the special sys_umem*() syscalls.
20 *
21 * Arguments are implemented via pointers to arguments. This not
22 * only increases the flexibility of syslet atoms (multiple syslets
23 * can share the same variable for example), but is also an
24 * optimization: copy_uatom() will only fetch syscall parameters
25 * up until the point it meets the first NULL pointer. 50% of all
26 * syscalls have 2 or less parameters (and 90% of all syscalls have
27 * 4 or less parameters).
28 *
29 * [ Note: since the argument array is at the end of the atom, and the
30 * kernel will not touch any argument beyond the final NULL one, atoms
31 * might be packed more tightly. (the only special case exception to
32 * this rule would be SKIP_TO_NEXT_ON_STOP atoms, where the kernel will
33 * jump a full syslet_uatom number of bytes.) ]
34 */
35struct syslet_uatom {
36 unsigned long flags;
37 unsigned long nr;
38 long __user *ret_ptr;
39 struct syslet_uatom __user *next;
40 unsigned long __user *arg_ptr[6];
41 /*
42 * User-space can put anything in here, kernel will not
43 * touch it:
44 */
45 void __user *private;
46};
47
48/*
49 * Flags to modify/control syslet atom behavior:
50 */
51
52/*
53 * Immediately queue this syslet asynchronously - do not even
54 * attempt to execute it synchronously in the user context:
55 */
56#define SYSLET_ASYNC 0x00000001
57
58/*
59 * Never queue this syslet asynchronously - even if synchronous
60 * execution causes a context-switching:
61 */
62#define SYSLET_SYNC 0x00000002
63
64/*
65 * Do not queue the syslet in the completion ring when done.
66 *
67 * ( the default is that the final atom of a syslet is queued
68 * in the completion ring. )
69 *
70 * Some syscalls generate implicit completion events of their
71 * own.
72 */
73#define SYSLET_NO_COMPLETE 0x00000004
74
75/*
76 * Execution control: conditions upon the return code
77 * of the previous syslet atom. 'Stop' means syslet
78 * execution is stopped and the atom is put into the
79 * completion ring:
80 */
81#define SYSLET_STOP_ON_NONZERO 0x00000008
82#define SYSLET_STOP_ON_ZERO 0x00000010
83#define SYSLET_STOP_ON_NEGATIVE 0x00000020
84#define SYSLET_STOP_ON_NON_POSITIVE 0x00000040
85
86#define SYSLET_STOP_MASK \
87 ( SYSLET_STOP_ON_NONZERO | \
88 SYSLET_STOP_ON_ZERO | \
89 SYSLET_STOP_ON_NEGATIVE | \
90 SYSLET_STOP_ON_NON_POSITIVE )
91
92/*
93 * Special modifier to 'stop' handling: instead of stopping the
94 * execution of the syslet, the linearly next syslet is executed.
95 * (Normal execution flows along atom->next, and execution stops
96 * if atom->next is NULL or a stop condition becomes true.)
97 *
98 * This is what allows true branches of execution within syslets.
99 */
100#define SYSLET_SKIP_TO_NEXT_ON_STOP 0x00000080
101
102/*
103 * This is the (per-user-context) descriptor of the async completion
104 * ring. This gets registered via sys_async_register().
105 */
106struct async_head_user {
107 /*
108 * Pointers to completed async syslets (i.e. syslets that
109 * generated a cachemiss and went async, returning -EASYNCSYSLET
110 * to the user context by sys_async_exec()) are queued here.
111 * Syslets that were executed synchronously are not queued here.
112 *
113 * Note: the final atom that generated the exit condition is
114 * queued here. Normally this would be the last atom of a syslet.
115 */
116 struct syslet_uatom __user **completion_ring;
117 /*
118 * Ring size in bytes:
119 */
120 unsigned long ring_size_bytes;
121
122 /*
123 * Maximum number of asynchronous contexts the kernel creates.
124 *
125 * -1UL has a special meaning: the kernel manages the optimal
126 * size of the async pool.
127 *
128 * Note: this field should be valid for the lifetime of async
129 * processing, because future kernels detect changes to this
130 * field. (enabling user-space to control the size of the async
131 * pool in a low-overhead fashion)
132 */
133 unsigned long max_nr_threads;
134};
135
136#endif