lowlatency patch question

[shai]

Hi,

I think the following is a bug that can affect kernels patched with
lowlatency, such as Audio? and RedHat AS2.1.

lowlatency patch added conditional_schedule() to be called from
close_files(?) at kernel/exit.c, which seems to raise a problem if the
process had LDT entries.
If it had LDT, at the stage of close_files(?) the tsk->mm already zeroed
(__exit_mm(?), which comes before __exit_files(?) in do_exit(?)).  If
conditional_schedule() at close_files(?) will succeed, switching back into
this process (that now have zeroed tsk->mm) will fail since the kernel will
not use the right LDT (since tsk->mm was zeroed, so switch_mm(?) will not be
called to load the LDT at schedule()).

Switching back to a process that had a register that used the LDT will fail
since the register probably points to non-valid LDT entry (since we are
using the wrong LDT), which will lead to a segmentation fault.
 
--Shai


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/