Hi: What is the original purpose of uid of semaphore? On Fri, Dec 26, 2008 at 3:09 PM, shark huang <[email protected]> wrote:
> Hi: > > On Fri, Dec 26, 2008 at 2:44 PM, ajit mote <[email protected]>wrote: > >> 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 >> >>> > Yes, Yes. So I confuse what does mean the uid for? > >> >>>> >>>> >>>>>>>> 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 >> >> >
