Messages in this thread | | | Date | Fri, 28 Jul 2006 10:52:10 -0400 | From | Theodore Tso <> | Subject | Re: A better interface, perhaps: a timed signal flag |
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On Fri, Jul 28, 2006 at 09:33:26AM -0400, Steven Rostedt wrote: > What you could have is this: > > volatile int *flag; > > register_timeout(&time_val, &flag); > while (work_to_do()) { > do_a_bit_of_work(); > if (*flag) > break; > } > > Where the kernel would register a location to set a timeout with, and > the kernel would setup a flag for you and then map it into userspace. > Perhaps only allow one flag per task and place it as a field of the task > structure. There's no reason that the tasks own task sturct cant be > mapped read only to user space, is there?
Good point, and limiting this facility to one such timeout per task_struct seems like a reasonable restriction. The downsides I can see about about mapping the tasks' own task struct would be (a) a potential security leak either now or in the future if some field in the task_struct shouldn't be visible to a non-privileged userspace program, and (b) exposing the task_struct might cause some (stupid) programs to depend on the task_struct layout. Allocating an otherwise empty 4k page just for this purpose wouldn't be all that horrible, though, and would avoid these potential problems.
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