Bug#561203: threads and fork on machine with VIPT-WB cache
On Wed, 02 Jun 2010, Modestas Vainius wrote:
> this bug  is back to the "very common" department with eglibc 2.11 (libc6-
> dev_2.11.1-1) builds. Majority of KDE applications are failing to build on
> hppa again. Is there really nothing what could be done to fix it?
I will just say it is very tricky. I think a fix is possible (arm and mips
had similar cache problems) but the victim replacement present in PA8800/PA8900
caches makes the problem especially difficult for hardware using these
I have spent the last few months testing various alternatives and have
now done hundreds of kernel builds. I did post some experimental patches
that fix the problem on UP kernels. However, the problem is not resolved
for SMP kernels.
The minifail test is a good one to demonstrate the problem. Indeed,
a very similar test was given in the thread below:
This thread also discusses the PA8800 problem:
I currently surmise that we have a problem with the cache victim
replacement, although the cause isn't clear. I did find recently
that the cache prefetch in copy_user_page_asm extends to the line
beyond the end of the page, but fixing this doesn't resolve the problem.
I am still experimenting with using equivalent aliasing. It does
help to flush in ptep_set_wrprotect.
J. David Anglin email@example.com
National Research Council of Canada (613) 990-0752 (FAX: 952-6602)