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OS-2366 ddi_periodic_add(9F) is entirely rubbish
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--- old/usr/src/man/man9f/ddi_periodic_delete.9f
+++ new/usr/src/man/man9f/ddi_periodic_delete.9f
1 1 '\" te
2 +.\" Copyright 2013, Joyent, Inc. All Rights Reserved.
2 3 .\" Copyright (c) 2009, Sun Microsystems, Inc. All Rights Reserved
3 4 .\" The contents of this file are subject to the terms of the Common Development and Distribution License (the "License"). You may not use this file except in compliance with the License. You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing.
4 5 .\" See the License for the specific language governing permissions and limitations under the License. When distributing Covered Code, include this CDDL HEADER in each file and include the License file at usr/src/OPENSOLARIS.LICENSE. If applicable, add the following below this CDDL HEADER, with
5 6 .\" the fields enclosed by brackets "[]" replaced with your own identifying information: Portions Copyright [yyyy] [name of copyright owner]
6 -.TH DDI_PERIODIC_DELETE 9F "May 6, 2009"
7 +.TH DDI_PERIODIC_DELETE 9F "Jul 23, 2013"
7 8 .SH NAME
8 -ddi_periodic_delete \- cancel nanosecond periodic timeout requests
9 +ddi_periodic_delete \- cancel periodic function invocation requests
9 10 .SH SYNOPSIS
10 11 .LP
11 12 .nf
12 13 #include <sys/dditypes.h>
13 14 #include <sys/sunddi.h>
14 15
15 -\fBvoid\fR \fBddi_periodic_delete\fR(\fBddi_periodic_t\fR \fIreq\fR\fB);\fR
16 +\fBvoid\fR \fBddi_periodic_delete\fR(\fBddi_periodic_t\fR \fIrequest\fR\fB);\fR
16 17 .fi
17 18
18 19 .SH INTERFACE LEVEL
19 20 .sp
20 21 .LP
21 22 Solaris DDI specific (Solaris DDI)
22 23 .SH PARAMETERS
23 24 .sp
24 25 .ne 2
25 26 .na
26 -\fB\fIreq\fR\fR
27 +\fB\fIrequest\fR\fR
27 28 .ad
28 29 .RS 7n
29 30 \fBddi_periodic_t\fR opaque value returned by \fBddi_periodic_add\fR(9F)
30 31 .RE
31 32
32 33 .SH DESCRIPTION
33 34 .sp
34 35 .LP
35 -The \fBddi_periodic_delete()\fR function cancels the \fBddi_periodic_add\fR(9F)
36 -request that was previously issued.
36 +The \fBddi_periodic_delete()\fR function cancels a periodic invocation request
37 +previously established with \fBddi_periodic_add\fR(9F).
37 38 .sp
38 39 .LP
39 -As with \fBuntimeout\fR(9F), calling \fBddi_periodic_delete()\fR against a
40 -periodic \fItimeout\fR request which is either running on another CPU, or has
41 -already been canceled causes no problems. Unlike \fBuntimeout\fR(9F), there are
42 -no restrictions on the lock which might be held across the call to
43 -\fBddi_periodic_delete()\fR.
40 +It is not possible to cancel a periodic invocation request from within the
41 +periodic callback itself; to do so is a programming error that will panic the
42 +system. Instead, requests must be cancelled from some other user or kernel
43 +context routine, such as the \fBdetach\fR(9E) entry point of a module.
44 +.sp
45 +.LP
46 +If the callback function is already executing (for instance, on another CPU)
47 +when the request is cancelled, \fBddi_periodic_delete()\fR will block until
48 +it finishes executing and is completely unregistered. The callback will not
49 +be invoked again after the call to \fBddi_periodic_delete()\fR returns.
44 50 .SH CONTEXT
45 51 .sp
46 52 .LP
47 53 The \fBddi_periodic_delete()\fR function may be called from user or kernel
48 54 context.
49 55 .SH EXAMPLES
50 56 .LP
51 -\fBExample 1 \fRCancelling a timeout request
57 +\fBExample 1 \fRCancelling a periodic invocation request
52 58 .sp
53 59 .LP
54 -In the following example, the device driver cancels the \fItimeout\fR request
55 -by calling \fBddi_periodic_delete()\fR against the request that was previously
56 -issued.
60 +In the following example, the device driver cancels the request
61 +by calling \fBddi_periodic_delete()\fR and passing the opaque \fIrequest\fR
62 +identifier returned by a previous call to \fBddi_periodic_add\fR(9F).
57 63
58 64 .sp
59 65 .in +2
60 66 .nf
61 67 /*
62 -* Stop the periodic timer
63 -*/
68 + * Stop the periodic timer.
69 + */
64 70 static void
65 71 stop_periodic_timer(struct my_state *statep)
66 72 {
67 - ddi_periodic_delete(statep->periodic_id);
68 - delay(1); /* wait for one tick */
69 - mutex_destory(&statep->lock);
73 + ddi_periodic_delete(statep->periodic_id);
74 + mutex_destroy(&statep->lock);
70 75 }
71 76
72 77 static void
73 78 start_periodic_timer(struct my_state *statep)
74 79 {
75 - hrtime_t interval = CHECK_INTERVAL;
80 + hrtime_t interval = CHECK_INTERVAL;
76 81
77 - mutex_init(&statep->lock, NULL, MUTEX_DRIVER,
78 - (void *)DDI_IPL_0);
82 + mutex_init(&statep->lock, NULL, MUTEX_DRIVER, DDI_IPL_0);
79 83
80 - /*
81 - * Register my_callback which is invoked periodically
82 - * in CHECK_INTERVAL in kernel context.
83 - */
84 - statep->periodic_id = ddi_periodic_add(my_periodic_func,
85 - statep, interval, DDI_IPL_0);
84 + /*
85 + * Register my_callback which is invoked periodically
86 + * in CHECK_INTERVAL in kernel context.
87 + */
88 + statep->periodic_id = ddi_periodic_add(my_periodic_func,
89 + statep, interval, DDI_IPL_0);
86 90 }
87 91
88 92 static void
89 93 my_periodic_func(void *arg)
90 94 {
91 - /*
92 - * This handler is invoked periodically.
93 - */
94 - struct my_state *statep = (struct my_state *)arg;
95 + /*
96 + * This handler is invoked periodically.
97 + */
98 + struct my_state *statep = (struct my_state *)arg;
95 99
96 - mutex_enter(&statep->lock);
97 - if (load_unbalanced(statep)) {
98 - balance_tasks(statep);
99 - }
100 - mutex_exit(&statep->lock);
100 + mutex_enter(&statep->lock);
101 + if (load_unbalanced(statep)) {
102 + balance_tasks(statep);
103 + }
104 + mutex_exit(&statep->lock);
101 105 }
102 106 .fi
103 107 .in -2
104 108
105 109 .SH SEE ALSO
106 110 .sp
107 111 .LP
108 112 \fBcv_timedwait\fR(9F), \fBddi_intr_get_pri\fR(9F), \fBddi_periodic_add\fR(9F),
109 -\fBdelay\fR(9F), \fBdrv_usectohz\fR(9F), \fBqtimeout\fR(9F),
110 -\fBquntimeout\fR(9F), \fBtimeout\fR(9F), \fBuntimeout\fR(9F)
113 +\fBqtimeout\fR(9F), \fBquntimeout\fR(9F), \fBtimeout\fR(9F), \fBuntimeout\fR(9F)
111 114 .SH NOTES
112 115 .sp
113 116 .LP
114 -There might be a race between a callback invocation and
115 -\fBddi_periodic_delete()\fR. A device driver should take a responsibility for
116 -this avoidance if needed by using the kernel synchronization such as a mutex
117 -lock or calling \fBdelay\fR(9F) as in the example above.
117 +Historically this interface was advertised as safe for use from within the
118 +periodic callback function. In order to ensure the correct operation of the
119 +system, and as reflected in the documentation above, this unlikely (and
120 +unsafe) usage pattern is no longer allowed.
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