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1.1 root 1:
2:
3: semop() COHERENT System Call semop()
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8: Perform semaphore operations
9:
10: #include <sys/sem.h>
11: sseemmoopp(_s_e_m_i_d, _s_o_p_s, _n_s_o_p_s)
12: iinntt _s_e_m_i_d, _n_s_o_p_s; ssttrruucctt sseemmbbuuff(_s_o_p_s)[];
13:
14: semop can atomically perform a number of operations on the set of
15: semaphores associated with the semaphore identifier semid. sops
16: pointer to the array of semaphore-operation structures. nsops is
17: the number of such structures in the array. Each structure in-
18: cludes the following members:
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20:
21: short sem_num; /* semaphore number */
22: short sem_op; /* semaphore operation */
23: short sem_flg; /* operation flags */
24:
25:
26: Each semaphore operation specified by sem_op is performed on the
27: semaphore specified by semid and sem_num.
28:
29: sem_op specifies one of three semaphore operations, as follows:
30:
31: * If sem_op is negative, one of the following occurs:
32:
33: 11. If semval is greater than or equal to the absolute value of
34: sem_op, the absolute value of sem_op is subtracted from sem-
35: val.
36:
37: 22. If semval is less than the absolute value of sem_op and
38: (_s_e_m__f_l_g & IIPPCC_NNOOWWAAIITT) is true, semop sets errno to EGAIN and
39: returns -1.
40:
41: 33. If semval is less than the absolute value of sem_op and
42: (_s_e_m__f_l_g & IIPPCC_NNOOWWAAIITT) is false, semop increments the semncnt
43: associated with the specified semaphore and suspend execution
44: of the calling process until one of the following occurs:
45:
46: aa. semval becomes greater than or equal to the absolute value of
47: _s_e_m__o_p. When this occurs, the value of semncnt associated
48: with the specified semaphore is decremented, and the absolute
49: value of sem_op is subtracted from semval.
50:
51: bb. The semid for which the calling process is awaiting action is
52: removed from the system.
53:
54: cc. The calling process receives a signal. When this occurs, the
55: value of semncnt associated with the specified semaphore is
56: decremented, and the calling process resumes execution in the
57: manner prescribed in signal.
58:
59: * If sem_op is positive, the value of sem_op is added to semval.
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64: COHERENT Lexicon Page 1
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68:
69: semop() COHERENT System Call semop()
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71:
72:
73: * If sem_op is zero, one of the following occurs:
74:
75: 11. If semval is zero, semop returns immediately.
76:
77: 22. If semval does not equal zero and (_s_e_m__f_l_g & IIPPCC_NNOOWWAAIITT) is
78: true, semop immediately returns -1, with eerrrrnnoo set to EGAIN.
79:
80: 33. If semval is not equal to zero and (_s_e_m__f_l_g & IIPPCC_NNOOWWAAIITT) is
81: false, semop increments the semzcnt associated with the
82: specified semaphore and suspends execution of the calling
83: process until one of the following occurs:
84:
85: aa. semval becomes zero, at which time the value of semzcnt as-
86: sociated with the specified semaphore is decremented.
87:
88: bb. The semid for which the calling process is awaiting action is
89: removed from the system.
90:
91: cc. The calling process receives a signal. When this occurs, the
92: value of semzcnt associated with the specified semaphore is
93: decremented, and the calling process resumes execution in the
94: manner prescribed in signal.
95:
96: semop fails if one or more of the following are true for any of
97: the semaphore operations specified by sops:
98:
99: * semid is not a valid semaphore identifier. semop sets errno
100: to EINVAL
101:
102: * sem_num is less than zero or greater than or equal to the num-
103: ber of semaphores in the set associated with semid (EEFFBBIIGG).
104:
105: * nsops is greater than the system imposed maximum (EE22BBIIGG).
106:
107: * Operation permission is denied to the calling process
108: (EEAACCCCEESS).
109:
110: * The operation would result in suspension of the calling
111: process but (_s_e_m__f_l_g & IIPPCC_NNOOWWAAIITT) is true (EEAAGGAAIINN).
112:
113: * An operation would cause a semval to overflow the system im-
114: posed limit (EERRAANNGGEE).
115:
116: * sops points to an illegal address (EEFFAAUULLTT).
117:
118: Upon successful completion, the value of sempid for each
119: semaphore specified in the array pointed to by sops is set equal
120: to the process identifier of the calling process.
121:
122: ***** Return Value *****
123:
124: If semop returns due to the receipt of a signal, it returns -1 to
125: the calling process and sets errno to EINTR. If it returns due
126: to the removal of a semid from the system, it returns -1 and sets
127: errno to EDOM.
128:
129:
130: COHERENT Lexicon Page 2
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133:
134:
135: semop() COHERENT System Call semop()
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137:
138:
139:
140: Upon successful completion, semop returns the value of semval at
141: the time of the call for the last operation in the array pointed
142: to by sops. Otherwise, it returns -1 and sets errno to an ap-
143: propriate value.
144:
145: ***** Files *****
146:
147: /usr/include/sys/ipc.h
148: /usr/include/sys/sem.h
149: /dev/sem
150: /drv/sem
151:
152: ***** See Also *****
153:
154: COHERENT system calls, sem, semctl(), semget()
155:
156: ***** Notes *****
157:
158: The flag SEM_UNDO is not supported. This flag would allow
159: semaphore operations to be undone upon the termination of the
160: process which performed the operations.
161:
162: To improve portability, the COHERENT system implements semaphore
163: operations as a device driver rather than as an actual system
164: call.
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196: COHERENT Lexicon Page 3
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