Correct io_u_*_complete() return checking
[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#ifndef __user
14# define __user
15#endif
16
17/*
18 * This is the 'Syslet Atom' - the basic unit of execution
19 * within the syslet framework. A syslet always represents
20 * a single system-call plus its arguments, plus has conditions
21 * attached to it that allows the construction of larger
22 * programs from these atoms. User-space variables can be used
23 * (for example a loop index) via the special sys_umem*() syscalls.
24 *
25 * Arguments are implemented via pointers to arguments. This not
26 * only increases the flexibility of syslet atoms (multiple syslets
27 * can share the same variable for example), but is also an
28 * optimization: copy_uatom() will only fetch syscall parameters
29 * up until the point it meets the first NULL pointer. 50% of all
30 * syscalls have 2 or less parameters (and 90% of all syscalls have
31 * 4 or less parameters).
32 *
33 * [ Note: since the argument array is at the end of the atom, and the
34 * kernel will not touch any argument beyond the final NULL one, atoms
35 * might be packed more tightly. (the only special case exception to
36 * this rule would be SKIP_TO_NEXT_ON_STOP atoms, where the kernel will
37 * jump a full syslet_uatom number of bytes.) ]
38 */
39struct syslet_uatom {
40 unsigned long flags;
41 unsigned long nr;
42 long __user *ret_ptr;
43 struct syslet_uatom __user *next;
44 unsigned long __user *arg_ptr[6];
45 /*
46 * User-space can put anything in here, kernel will not
47 * touch it:
48 */
49 void __user *private;
50};
51
52/*
53 * Flags to modify/control syslet atom behavior:
54 */
55
56/*
57 * Immediately queue this syslet asynchronously - do not even
58 * attempt to execute it synchronously in the user context:
59 */
60#define SYSLET_ASYNC 0x00000001
61
62/*
63 * Never queue this syslet asynchronously - even if synchronous
64 * execution causes a context-switching:
65 */
66#define SYSLET_SYNC 0x00000002
67
68/*
69 * Do not queue the syslet in the completion ring when done.
70 *
71 * ( the default is that the final atom of a syslet is queued
72 * in the completion ring. )
73 *
74 * Some syscalls generate implicit completion events of their
75 * own.
76 */
77#define SYSLET_NO_COMPLETE 0x00000004
78
79/*
80 * Execution control: conditions upon the return code
81 * of the previous syslet atom. 'Stop' means syslet
82 * execution is stopped and the atom is put into the
83 * completion ring:
84 */
85#define SYSLET_STOP_ON_NONZERO 0x00000008
86#define SYSLET_STOP_ON_ZERO 0x00000010
87#define SYSLET_STOP_ON_NEGATIVE 0x00000020
88#define SYSLET_STOP_ON_NON_POSITIVE 0x00000040
89
90#define SYSLET_STOP_MASK \
91 ( SYSLET_STOP_ON_NONZERO | \
92 SYSLET_STOP_ON_ZERO | \
93 SYSLET_STOP_ON_NEGATIVE | \
94 SYSLET_STOP_ON_NON_POSITIVE )
95
96/*
97 * Special modifier to 'stop' handling: instead of stopping the
98 * execution of the syslet, the linearly next syslet is executed.
99 * (Normal execution flows along atom->next, and execution stops
100 * if atom->next is NULL or a stop condition becomes true.)
101 *
102 * This is what allows true branches of execution within syslets.
103 */
104#define SYSLET_SKIP_TO_NEXT_ON_STOP 0x00000080
105
106/*
107 * This is the (per-user-context) descriptor of the async completion
108 * ring. This gets registered via sys_async_register().
109 */
110struct async_head_user {
111 /*
112 * Pointers to completed async syslets (i.e. syslets that
113 * generated a cachemiss and went async, returning -EASYNCSYSLET
114 * to the user context by sys_async_exec()) are queued here.
115 * Syslets that were executed synchronously are not queued here.
116 *
117 * Note: the final atom that generated the exit condition is
118 * queued here. Normally this would be the last atom of a syslet.
119 */
120 struct syslet_uatom __user **completion_ring;
121 /*
122 * Ring size in bytes:
123 */
124 unsigned long ring_size_bytes;
125
126 /*
127 * Maximum number of asynchronous contexts the kernel creates.
128 *
129 * -1UL has a special meaning: the kernel manages the optimal
130 * size of the async pool.
131 *
132 * Note: this field should be valid for the lifetime of async
133 * processing, because future kernels detect changes to this
134 * field. (enabling user-space to control the size of the async
135 * pool in a low-overhead fashion)
136 */
137 unsigned long max_nr_threads;
138};
139
140#endif