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618febd678
Fix the alloc_slabmgmt panic Hopefully this should also fix a lot of other intermittent kernel bugs. The problem has been around since 2.6.9-rc2-pa6 when we allowed floating point registers to be used in kernel code. The essence of the problem is that gcc prefers to use floating point for integer divides and multiples. Further, it can rely on the values in the no clobber fp regs being correct across a function call. Unfortunately, our task switch function only saves the integer no clobber registers, not the fp ones, so if gcc makes a function call to any function in the kernel which could sleep, the values it is relying on in any no clobber floating point register may be lost. In the case of alloc_slabmgmt, the value of the page offset is being stored in %fr12 across a call to kmem_getpages(), which sleeps if no pages are available. Thus, the offset can be trashed and the slab code can end up with a completely bogus address leading to corruption. Kudos to Randolph who came up with the program to trip this problem at will and thus allowed it to be tracked and fixed. Signed-off-by: James Bottomley <jejb@parisc-linux.org> Signed-off-by: Kyle McMartin <kyle@parisc-linux.org> |
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