On Tue, 18 Oct 2016, Martin Schwidefsky wrote: > On Tue, 18 Oct 2016 00:16:13 +0200 > Arnd Bergmann <a...@arndb.de> wrote: > > > gcc correctly warns about an incorrect use of the 'pa' variable > > in case we pass an empty scatterlist to __s390_dma_map_sg: > > > > arch/s390/pci/pci_dma.c: In function '__s390_dma_map_sg': > > arch/s390/pci/pci_dma.c:309:13: warning: 'pa' may be used uninitialized in > > this function [-Wmaybe-uninitialized] > > > > This adds a bogus initialization to the function to sanitize > > the debug output. I would have preferred a solution without > > the initialization, but I only got the report from the > > kbuild bot after turning on the warning again, and didn't > > manage to reproduce it myself. > > > > Signed-off-by: Arnd Bergmann <a...@arndb.de> > > --- > > arch/s390/pci/pci_dma.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/arch/s390/pci/pci_dma.c b/arch/s390/pci/pci_dma.c > > index 7350c8b..6b2f72f 100644 > > --- a/arch/s390/pci/pci_dma.c > > +++ b/arch/s390/pci/pci_dma.c > > @@ -423,7 +423,7 @@ static int __s390_dma_map_sg(struct device *dev, struct > > scatterlist *sg, > > dma_addr_t dma_addr_base, dma_addr; > > int flags = ZPCI_PTE_VALID; > > struct scatterlist *s; > > - unsigned long pa; > > + unsigned long pa = 0; > > int ret; > > > > size = PAGE_ALIGN(size); > > The compiler is right. pa is set in the for-loop. If "dma_addr < > dma_addr_base + size" > is never true and __dma_purge_tlb() returns with an error, pa *is* > uninitialized. > The fix seems sensible to me.
Although that could only happen if map_sg is called with zero length sg list entries I'm in favor getting rid of that warning. Acked-by: Sebastian Ott <seb...@linux.vnet.ibm.com> Regards, Sebastian
