On Wed, Jun 14, 2017 at 02:13:28PM +0200, Florian Weimer wrote:
> Occasionally, when using the “time” bash built-in, I get bogus output,
> like this:
>
> real 0m34.671s
> user 0m24.755s
> sys .+(.0*-)m,/.222s
>
> real 0m23.049s
> user 0m15.599s
> sys 153122387m27.677s
>
> This is not corruption caused by concurrently running programs, it's
> actually what bash prints, as shown by strace:
...
> I see this with kernel-4.11.0-2.fc26.s390x from Fedora. This could be a
> regression because I have never noticed it before when running the glibc
> testsuite under earlier kernels.
Thank you for the bug report. This should have been fixed with git commit
07a63cbe8bcb ("s390/cputime: fix incorrect system time"). This has only
been recently merged and is marked for stable kernel backports. With that
fix it seems to work.
commit 07a63cbe8bcb6ba72fb989dcab1ec55ec6c36c7e
Author: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Date: Tue May 2 13:36:00 2017 +0200
s390/cputime: fix incorrect system time
git commit c5328901aa1db134 "[S390] entry[64].S improvements" removed
the update of the exit_timer lowcore field from the critical section
cleanup of the .Lsysc_restore/.Lsysc_done and .Lio_restore/.Lio_done
blocks. If the PSW is updated by the critical section cleanup to point to
user space again, the interrupt entry code will do a vtime calculation
after the cleanup completed with an exit_timer value which has *not* been
updated. Due to this incorrect system time deltas are calculated.
If an interrupt occured with an old PSW between .Lsysc_restore/.Lsysc_done
or .Lio_restore/.Lio_done update __LC_EXIT_TIMER with the system entry
time of the interrupt.
Cc: stable@xxxxxxxxxxxxxxx # 3.3+
Tested-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
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