Messages in this thread |  | | | Date | Tue, 15 Dec 1998 17:07:21 +1300 | | From | Stephen Donnelly <> | | Subject | clock broken at interrupts still (131AC11) |
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It seems that the kernel time is not monotonically increasing in recent (i386) kernels.
2.1.126 introduced a bug that is still present in 2.1.131 and also the AC11 patches. Code that records the time during the top half of an interrupt may get a timestamp that is exactly 10000 microseconds back in time from when it should be. An easy way to see this is to use tcpdump on a reasonably busy network (500 to 1000 packets per second), and examine the usec portion of the packet timestamp. This is affected because the timestamp is recorded during interrupt time (netif_rx in linux/net/core/dev.c).
See this URL for more details and graphs:
http://atm.cs.waikato.ac.nz/~sfd/bug/
Stephen. -- ----------------------------------------------------------------------- Stephen Donnelly (BCMS) email: sfd@cs.waikato.ac.nz Waikato ATM Group Lab G1.31 phone +64 7 838 4466 x6728 Computer Science Department, University of Waikato, New Zealand ----------------------------------------------------------------------- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/
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