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| author | Jeremy Fitzhardinge <jeremy@xensource.com> | 2007-07-17 18:37:06 -0700 |
|---|---|---|
| committer | Jeremy Fitzhardinge <jeremy@goop.org> | 2007-07-18 08:47:44 -0700 |
| commit | 8b84ad942b534f8faeb34b68f0f7277ea375fed0 (patch) | |
| tree | 911472add5b9068a95a77215a70dac63edf6202e /Documentation/robust-futex-ABI.txt | |
| parent | d66bf8fcf3fce058a1cd164a7c8ee6093fdf039c (diff) | |
xen: hack to prevent bad segment register reload
The hypervisor saves and restores the segment registers as part of the
state is saves while context switching. If, during a context switch,
the next process doesn't use the TLS segments, it invalidates the GDT
entry, causing the segment register reload to fault. This fault
effectively doubles the cost of a context switch.
This patch is a band-aid workaround which clears the usermode %gs
after it has been saved for the previous process, but before it gets
reloaded for the next, and it avoids having the hypervisor attempt to
erroneously reload it.
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Diffstat (limited to 'Documentation/robust-futex-ABI.txt')
0 files changed, 0 insertions, 0 deletions