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All Rights Reserved. 44 .\" Portions Copyright (c) 2008, Sun Microsystems, Inc. All Rights Reserved. 45 .\" 46 .TH SEM_TIMEDWAIT 3C "Feb 5, 2008" 47 .SH NAME 48 sem_timedwait, sem_reltimedwait_np \- lock a semaphore 49 .SH SYNOPSIS 50 .LP 51 .nf 52 #include <semaphore.h> 53 #include <time.h> 54 55 \fBint\fR \fBsem_timedwait\fR(\fBsem_t *restrict\fR \fIsem\fR, 56 \fBconst struct timespec *restrict\fR \fIabs_timeout\fR); 57 .fi 58 59 .LP 60 .nf 61 \fBint\fR \fBsem_reltimedwait_np\fR(\fBsem_t *restrict\fR \fIsem\fR, 62 \fBconst struct timespec *restrict\fR \fIrel_timeout\fR); 63 .fi 64 65 .SH DESCRIPTION 66 .LP 67 The \fBsem_timedwait()\fR function locks the semaphore referenced by \fIsem\fR 68 as in the \fBsem_wait\fR(3C) function. However, if the semaphore cannot be 69 locked without waiting for another process or thread to unlock the semaphore by 70 performing a \fBsem_post\fR(3C) function, this wait is terminated when the 71 specified timeout expires. 72 .sp 73 .LP 74 The \fBsem_reltimedwait_np()\fR function is identical to the 75 \fBsem_timedwait()\fR function, except that the timeout is specified as a 76 relative time interval. 77 .sp 78 .LP 79 For \fBsem_timedwait()\fR, the timeout expires when the absolute time specified 80 by \fIabs_timeout\fR passes, as measured by the \fBCLOCK_REALTIME\fR clock 81 (that is, when the value of that clock equals or exceeds \fIabs_timeout\fR), or 82 if the absolute time specified by \fIabs_timeout\fR has already been passed at 83 the time of the call. 84 .sp 85 .LP 86 For \fBsem_reltimedwait_np()\fR, the timeout expires when the time interval 87 specified by \fIrel_timeout\fR passes, as measured by the \fBCLOCK_REALTIME\fR 88 clock, or if the time interval specified by \fIrel_timeout\fR is negative at 89 the time of the call. 90 .sp 91 .LP 92 The resolution of the timeout is the resolution of the \fBCLOCK_REALTIME\fR 93 clock. The \fBtimespec\fR data type is defined as a structure in the 94 <\fBtime.h\fR> header. 95 .sp 96 .LP 97 Under no circumstance does the function fail with a timeout if the semaphore 98 can be locked immediately. The validity of the \fIabs_timeout\fR need not be 99 checked if the semaphore can be locked immediately. 100 .SH RETURN VALUES 101 .LP 102 The \fBsem_timedwait()\fR and \fBsem_reltimedwait_np()\fR functions return 0 if 103 the calling process successfully performed the semaphore lock operation on the 104 semaphore designated by \fIsem\fR. If the call was unsuccessful, the state of 105 the semaphore is be unchanged and the function returns -1 and sets \fBerrno\fR 106 to indicate the error. 107 .SH ERRORS 108 .LP 109 The \fBsem_timedwait()\fR and \fBsem_reltimedwait_np()\fR functions will fail 110 if: 111 .sp 112 .ne 2 113 .na 114 \fB\fBEINVAL\fR\fR 115 .ad 116 .RS 13n 117 The \fIsem\fR argument does not refer to a valid semaphore. 118 .RE 119 120 .sp 121 .ne 2 122 .na 123 \fB\fBEINVAL\fR\fR 124 .ad 125 .RS 13n 126 The process or thread would have blocked, and the timeout parameter specified a 127 nanoseconds field value less than zero or greater than or equal to 1,000 128 million. 129 .RE 130 131 .sp 132 .ne 2 133 .na 134 \fB\fBETIMEDOUT\fR\fR 135 .ad 136 .RS 13n 137 The semaphore could not be locked before the specified timeout expired. 138 .RE 139 140 .sp 141 .LP 142 The \fBsem_timedwait()\fR and \fBsem_reltimedwait_np()\fR functions may fail 143 if: 144 .sp 145 .ne 2 146 .na 147 \fB\fBEDEADLK\fR\fR 148 .ad 149 .RS 11n 150 A deadlock condition was detected. 151 .RE 152 153 .sp 154 .ne 2 155 .na 156 \fB\fBEINTR\fR\fR 157 .ad 158 .RS 11n 159 A signal interrupted this function. 160 .RE 161 162 .SH ATTRIBUTES 163 .LP 164 See \fBattributes\fR(5) for descriptions of the following attributes: 165 .sp 166 167 .sp 168 .TS 169 box; 170 c | c 171 l | l . 172 ATTRIBUTE TYPE ATTRIBUTE VALUE 173 _ 174 Interface Stability Committed 175 _ 176 MT-Level MT-Safe 177 _ 178 Standard See below. 179 .TE 180 181 .sp 182 .LP 183 For \fBsem_timedwait()\fR, see \fBstandards\fR(5). 184 .SH SEE ALSO 185 .LP 186 \fBsemctl\fR(2), \fBsemget\fR(2), \fBsemop\fR(2), \fBtime\fR(2), 187 \fBsem_post\fR(3C), \fBsem_trywait\fR(3C), \fBsem_wait\fR(3C), 188 \fBattributes\fR(5), \fBstandards\fR(5)