On Wed, Dec 3, 2008 at 7:08 PM, Dan Nelson <[EMAIL PROTECTED]> wrote: > In the last episode (Dec 03), Vlad GALU said: >> On Wed, Dec 3, 2008 at 5:23 PM, Dan Nelson <[EMAIL PROTECTED]> wrote: >> > In the last episode (Dec 03), Vlad GALU said: >> >> I'm running a statically linked binary, which I've built inside a >> >> jail. The jail's libc & co are in sync with the host's. Truss then >> >> shows this: >> >> >> >> -- cut here -- >> >> -- UNKNOWN SYSCALL 1048532 -- >> >> -- UNKNOWN SYSCALL 1048532 -- >> > >> > Is this a threaded app that you attached truss to after it was >> > started? The method that truss uses to catch syscall enter/exit >> > events doesn't indicate whether the event is an enter or an exit, >> > so if you attach while a syscall is active, truss handles the exit >> > event as if it were a syscall entry event, and never gets back in >> > synch. It gets worse with threaded apps because each thread is >> > another chance to get out of synch. Try this patch: >> >> You were right, this application was indeed threaded. The messages >> still occur, although at a slightly lower rate. One other thing >> that's not particularly helpful is this: >> >> -- cut here-- >> read(1074283119,"\M-Ry\^A\0",7356800) = 4 (0x4) >> -- and here -- >> >> I obviously don't have that many descriptors in my process. I can >> live with the malformed message, but it's a PITA not to know which fd >> the read was actually made from :( > > It looks like there's some other problem where truss either drops a > syscall event, or puts some status fields into the wrong thread's > structure. It seems to happen when two threads call blocking syscalls, > and when they return, truss gets confused as to which thread called > which syscall. The read syscall is probably still pending, and you're > getting the arguments of the syscall that returned, printed as if it > was the read syscall. When the read call completes, you'll probably > get an --UNKNOWN SYSCALL-- line, or another mismatched syscall output > line. > > An alternative it to use ktrace/kdump to trace the process; it's more > cumbersome to use, but doesn't have problems with threaded processes.
Now why didn't I think of that? :/ Thanks for the suggestion! -- ~/.signature: no such file or directory _______________________________________________ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "[EMAIL PROTECTED]"
