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 > >
