> > How can I know who own the semaphore at one moment? >>>>> >>>> >>>> ipcs -s >>>> >>> 'cat /proc/sysvipc/sem' should be same. >>> >>> >>>> >>>> >>>> >>>>> On Thu, Dec 25, 2008 at 12:26 AM, shark huang <[email protected]>wrote: >>>>> >>>>>> Hi: is the value of cuid and uid always same? Looks like they only >>>>>> are given a same value in function "ipc_addid", which means the value was >>>>>> initialized when the semaphore is created. >>>>>> >>>>> >> When performing the first task, the process which calls *semget*becomes >> the owner/creator, and Remember, ownership can be changed, but the >> creating process always remains the creator. So values of uid and cuid may >> not be always same. >> > Several user can operate one semaphore at the same time, so how to > decide who is the owner ? Could you show me in source code？ > >> Unfortunately, there isn't really a way to know what pid is "owning" the critical region that is being protected by this semaphore. This is because semaphores don't really enforce the notion of a critical section. Semaphores aren't binary gates, they aren't locked or unlocked (although they can be used that way). Its entirely possible for two processes to manipulate a semaphore in such a way as both complete the operation without blocking. So its not like the semphore defines a critical region by virtue solely of the call sites where it referenced. So the answer is no, there isn't a way to get what pids which are operating on the semaphore
> >> >> >>>>>> br >>>>>> shark >>>>>> >>>>>> >> Note: Please send mail to mailing list, this way everybody will be reading >> the thread >> >>> >>>>> >>>> >>>> >>>> -- >>>> Thanks & Regards, >>>> Ajit Subhash Mote >>>> >>>> >>> >> >> >> -- >> Thanks & Regards, >> Ajit Subhash Mote >> >> > -- Thanks & Regards, Ajit Subhash Mote
