On 03/17, Steven Rostedt wrote: > > On Sun, 2013-03-17 at 20:00 +0100, Oleg Nesterov wrote: > > On 03/17, Steven Rostedt wrote: > > > > > > > Change copy_process() to update the child's TIF_SYSCALL_TRACEPOINT > > > > under tasklist. > > > > > > Is this because "p = dup_task_struct(current);" is outside the lock? > > > Probably should state this in the change log. > > > > Not only, syscall_regfunc/syscall_unregfunc can miss the new child. > > > > Just suppose that syscall_regfunc() takes tasklist right before the > > forking task tries to take it for writing and and the child to the > > list. > > I'm a bit confused by the above. Maybe it's the typo with the "and and" > that's confusing me.
Yes, "and and" was supposed to be "and add". But probably I misunderstood you before... Well yes, this is because "p = dup_task_struct(current)" copies TIF_SYSCALL_TRACEPOINT outside of the tasklist-protected section which also makes the new task visible for do_each_thread(). IOW, the state of TIF_SYSCALL_TRACEPOINT bit can be correct after dup_task_struct(), but it can't be updated until copy_process() add the child to the list. > > OK, thanks, will do. But perhaps tracepoint_fork() would be better? > > tracepoint_fork() is similar to being called trace_fork() which would be > considered a tracepoint. Seeing tracepoint_fork() would make me think it > has something to do with the fork tracepoint. > > Do we plan on doing anything other than updating the syscall tracepoint > flag here? I find the "syscall_tracepoint_update()" very descriptive to > what is actually happening. While reading the fork code, seeing > 'syscall_tracepoint_update()' would tell me that this has something to > do with syscall tracepoints, which it does. But tracepoint_fork() would > have me think something completely different. OK, thanks, I am sending v2 in reply to v1. Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
