On 12 September 2017 at 18:47, Colin Ian King <colin.king@xxxxxxxxxxxxx> wrote: > On 12/09/17 18:42, Thomas Hellstrom wrote: >> Hi, Colin, >> >> On 09/12/2017 07:35 PM, Colin King wrote: >>> From: Colin Ian King <colin.king@xxxxxxxxxxxxx> >>> >>> mmap'ing the device multiple times will spam the kernel log with the >>> DRM_ERROR message about illegal mmap'ing the old fifo space. >> How are you hitting this? Multiple mappings should be fine as long as >> mapping offsets are correct, >> so hitting this message should indicate that the user-space app is doing >> something seriously wrong, and >> having it present in the log should probably help more than it hurts. >> >> /Thomas > > Good question. I hit similar issues with the drm qxl driver when > running some kernel regression tests with stress-ng [1]. I realize this > is an artificial test scenario so it is definitely not a typical > use-case, however, sync the illegal mmapping will return -EINVAL the > application will pick up that this is an error without the need of > spotting it in the kernel log. And a user space application can perform > many millions of these invalid mmaps causing kernel log spamming. > FWIW I'm the one to "blame" here - pointing Colin to drop the message. Two reasons come to mind: - there is a unwritten rule that roughly says "user input should not cause kernel log spam" - out of all the DRM drivers only QXL and VMWGFX print a message, with a patch addressing the former HTH Emil -- To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
