-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On Fri, 16 May 2003 10:45:12 +0200 "Joeri Belis" <joeri.belis@nollekens.be> wrote: >I looked at our timer and it is at : 1577504985 > >And if i understand correctly, this is a 32bit value and it can go >to: 4294967295. What will happen when we hit this limit? As you correctly said, jiffies is defined as unsigned long (which is a 32 bit value on x86 platforms) and it is incremented by one by do_timer() function every tick. In particular, you have HZ ticks per second with HZ = 100 on Intel x86 - kernel 2.4.x. This means you can experience a jiffy overflow. Kernel code is aware of this situation and so it handles it properly. If you write a device driver, probably sometimes you could be forced to do some checks even if it's rarely adopted. F.e. if you are measuring time intervals you could just think about a solution in which you evaluate the sign of delta = time_2 - time_1 If it is lesser than 0, jiffies has wrapped around and so in this case you can avoid problems doing this delta = (MAX_JIFFIES_VALUE - time_1) + time_2 thus obtaining something similar [..] delta = time_2 - time_1; if (delta < 0) delta += MAX_JIFFIES_VALUE; [..] Regards. - -- Angelo Dell'Aera 'buffer' Antifork Research, Inc. http://buffer.antifork.org PGP information in e-mail header -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.1 (GNU/Linux) iD8DBQE+xQ2gpONIzxnBXKIRAoHlAJ98TWYuTB1p12PhZVDZKaeJnrjJ4ACfUEMa 5Un8zC71YOrjNinaxRlnXTo= =IZQA -----END PGP SIGNATURE----- -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
