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authorIngo Molnar2009-07-10 21:38:02 +0200
committerIngo Molnar2009-07-10 22:18:45 +0200
commitf39d1b9792881ce4eb982ec8cc65258bf95674b5 (patch)
tree07f945a2a6f0b1f2fb2af759e386781d0e0bed3f /samples
parent2b8777ca0c944bf6498c45ed9c5c246bd63a719e (diff)
dma-debug: Fix the overlap() function to be correct and readable
Linus noticed how unclean and buggy the overlap() function is: - It uses convoluted (and bug-causing) positive checks for range overlap - instead of using a more natural negative check. - Even the positive checks are buggy: a positive intersection check has four natural cases while we checked only for three, missing the (addr < start && addr2 == end) case for example. - The variables are mis-named, making it non-obvious how the check was done. - It needlessly uses u64 instead of unsigned long. Since these are kernel memory pointers and we explicitly exclude highmem ranges anyway we cannot ever overflow 32 bits, even if we could. (and on 64-bit it doesnt matter anyway) All in one, this function needs a total revamp. I used Linus's suggestions minus the paranoid checks (we cannot overflow really because if we get totally bad DMA ranges passed far more things break in the systems than just DMA debugging). I also fixed a few other small details i noticed. Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Joerg Roedel <joerg.roedel@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'samples')
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