View Issue Details
| ID | Project | Category | View Status | Date Submitted | Last Update |
|---|---|---|---|---|---|
| 0000345 | 1003.1(2008)/Issue 7 | System Interfaces | public | 2010-10-28 23:31 | 2013-04-16 13:06 |
| Reporter | eblake | Assigned To | ajosey | ||
| Priority | normal | Severity | Objection | Type | Omission |
| Status | Closed | Resolution | Accepted As Marked | ||
| Name | Eric Blake | ||||
| Organization | Red Hat | ||||
| User Reference | ebb.semop | ||||
| Section | semop | ||||
| Page Number | 1840 | ||||
| Line Number | 58792 | ||||
| Interp Status | Approved | ||||
| Final Accepted Text | 0000345:0000615 | ||||
| Summary | 0000345: semop must update sem_otime | ||||
| Description | Historically, the sem_otime field associated with a semaphore tracks semop() actions, and the sem_ctime field tracks particular semctl() actions. The standard implies this is the case on lines 12708-12709 [XBD <sem.h>], but does not actually require it. In particular, this behavior must be enforced to avoid a data race, where one process creates a semaphore set and another obtains and acts on the set before the first can initialize the semaphore values. | ||||
| Desired Action | At both line 58514 [XSH semctl SETVAL] and line 58526 [SETALL], add a sentence before "Requires alter permission": Also, the sem_ctime variable of the semid_ds structure associated with semid shall be set to the current time. After line 58541 [semctl IPC_SET], add a sentence: The sem_ctime variable shall be set to the current time. At line 58796 [semop DESCRIPTION], add a sentence: Also, the sem_otime variable of the semid_ds structure associated with semid shall be set to the current time. | ||||
| Tags | tc1-2008 | ||||
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Interpretation response ----------------------- The standard clearly states that timestamps shall be updated, and conforming implementations must conform to this. Rationale: The description of IPC_STAT says: Place the current value of each member of the semid_ds data structure associated with semid into the structure pointed to by arg.buf, where arg is the fourth argument to semctl(). The contents of this structure are defined in <sys/sem.h>. and the definition of semid_ds in <sys/sem.h> includes these members: time_t sem_otime Last semop() time. time_t sem_ctime Last time changed by semctl(). Together these constitute a clear requirement for semctl() IPC_STAT to set the sem_otime member of arg.buf to the last time a semop() operation was performed on the semaphore, and to set the sem_ctime member of arg.buf to the last time the semaphore was changed by a semctl() call. However, the following edits will make it clear to the reader, as well as clarify that timestamps are truncated rather than rounded if the current time has more precision than time_t. Notes to the Editor (not part of this interpretation) ------------------- At line 17067 (XSH 2.7.1 IPC General Description), add a new paragraph: In addition to the ipc_perm structure, each associated data structure includes several time_t fields for recording timestamps of particular operations. When an operation is described as setting a timestamp to the current time, that particular timestamp member of the associated data structure shall be set to the largest time_t value which is not greater than the current time. At line 44077 [XSH msgctl IPC_SET], add: Also, the msg_ctime timestamp shall be set to the current time, as described in <ref to XSH 2.7.1>. At line 44145 [XSH msgget], change "set equal to the current time" to "set to the current time, as described in <ref to XSH 2.7.1>". At line 44230 [XSH msgrcv], change "set equal to the current time" to "set to the current time, as described in <ref to XSH 2.7.1>". At line 44329 [XSH msgsnd], change "set equal to the current time" to "set to the current time, as described in <ref to XSH 2.7.1>". At both line 58514 [XSH semctl SETVAL] and line 58526 [SETALL], add a sentence before "Requires alter permission": Also, the sem_ctime timestamp shall be set to the current time, as described in <ref to XSH 2.7.1>. After line 58541 [semctl IPC_SET], add a sentence: The sem_ctime timestamp shall be set to the current time, as described in <ref to XSH 2.7.1>. At line 58796 [semop DESCRIPTION], add a sentence: Also, the sem_otime timestamp shall be set to the current time, as described in <ref to XSH 2.7.1>. At line 60590 [shmat RETURN VALUE], add a sentence: Also, the shm_atime timestamp shall be set to the current time, as described in <ref to XSH 2.7.1>. At line 60648 [shmctl IPC_SET], add: Also, the shm_ctime timestamp shall be set to the current time, as described in <ref to XSH 2.7.1>. At line 60710 [shmdt RETURN VALUE], add a sentence: Also, the shm_dtime timestamp shall be set to the current time, as described in <ref to XSH 2.7.1>. At line 60760 [shmget], change "set equal to the current time" to "set to the current time, as described in <ref to XSH 2.7.1>". |
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Comments are due on this interpretation by January 16 2011 |
| Date Modified | Username | Field | Change |
|---|---|---|---|
| 2010-10-28 23:31 | eblake | New Issue | |
| 2010-10-28 23:32 | eblake | Status | New => Under Review |
| 2010-10-28 23:32 | eblake | Assigned To | => ajosey |
| 2010-10-28 23:32 | eblake | Name | => Eric Blake |
| 2010-10-28 23:32 | eblake | Organization | => Red Hat |
| 2010-10-28 23:32 | eblake | User Reference | => ebb.semop |
| 2010-10-28 23:32 | eblake | Section | => semop |
| 2010-10-28 23:32 | eblake | Page Number | => 1840 |
| 2010-10-28 23:33 | eblake | Line Number | => 58792 |
| 2010-10-28 23:33 | eblake | Interp Status | => --- |
| 2010-10-28 23:41 | eblake | Relationship added | related to 0000335 |
| 2010-11-11 16:14 | eblake | Note Added: 0000615 | |
| 2010-11-11 16:57 | eblake | Note Edited: 0000615 | |
| 2010-11-11 17:01 | eblake | Note Edited: 0000615 | |
| 2010-11-11 17:09 | eblake | Note Edited: 0000615 | |
| 2010-11-11 17:10 | eblake | Note Edited: 0000615 | |
| 2010-11-11 17:13 | geoffclare | Interp Status | --- => Pending |
| 2010-11-11 17:13 | geoffclare | Final Accepted Text | => 0000345:0000615 |
| 2010-11-11 17:13 | geoffclare | Status | Under Review => Interpretation Required |
| 2010-11-11 17:13 | geoffclare | Resolution | Open => Accepted As Marked |
| 2010-11-11 17:17 | geoffclare | Tag Attached: tc1-2008 | |
| 2010-12-16 16:13 | ajosey | Interp Status | Pending => Proposed |
| 2010-12-16 16:13 | ajosey | Note Added: 0000637 | |
| 2011-01-18 12:30 | ajosey | Interp Status | Proposed => Approved |
| 2013-04-16 13:06 | ajosey | Status | Interpretation Required => Closed |
