Description of problem: There were a few recent reports of tsc going back on LKML, as a result of which there could be cases when time (gettimeofday) jumps in the future. http://lkml.org/lkml/2007/8/23/96 http://lkml.org/lkml/2008/3/31/23 I did some kernel instrumentation on the recent RHEL5.1 kernel 2.6.18-53.1.19.el5, and see that read_tsc does jump back once in a while on my dual core box. As a result the value returned from read_tsc < clocksource->cycle_last value, which results in large values of offset due to the unsigned arithmetic involved (have a look at update_wall_time). Eventually results in some bogus gettimeofday values. There was a fix for this problem from Thomas Gleixner which was included in the 2.6.26-rc1 tree. http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=d8bb6f4c1670c8324e4135c61ef07486f7f17379 Attached is a backport of this fix. This is required on all RHEL kernels that use clocksource. Version-Release number of selected component (if applicable): How reproducible: Steps to Reproduce: 1. 2. 3. Actual results: Expected results: Additional info:
Created attachment 304882 [details] fix for tsc going back problem.
*** This bug has been marked as a duplicate of 443435 ***
(In reply to comment #2) > > *** This bug has been marked as a duplicate of 443435 *** I am not authorized to access that BUG, It says "You are not authorized to access bug #443435. Access to some bugs is restricted due to embargoed security issues or respect for customer and partner information which must remain confidential." Is there a way that I can look at that BUG ? Maybe you can add me to the CC list for bug #443435 ? Thanks, Alok
(In reply to comment #2) > > *** This bug has been marked as a duplicate of 443435 *** Prarit, Let me know if there is anyway to access that bug #443435.
Still need access to bug #443435 Need to know if you guys already have the fix and if so which kernel release is going to have that fix. Thanks, Alok (In reply to comment #3) > (In reply to comment #2) > > > > *** This bug has been marked as a duplicate of 443435 *** > > I am not authorized to access that BUG, > It says > > "You are not authorized to access bug #443435. > > Access to some bugs is restricted due to embargoed security issues or respect > for customer and partner information which must remain confidential." > > Is there a way that I can look at that BUG ? Maybe you can add me to the CC list > for bug #443435 ? > > Thanks, > Alok
Alok, the latest RHEL5 kernel has this patch. P. *** This bug has been marked as a duplicate of 443435 ***