On Tue, 2017-08-08 at 11:58 +0200, Florian Weimer wrote: > On 08/07/2017 08:23 PM, Mike Kravetz wrote: > > If my thoughts above are correct, what about returning EINVAL if > > one > > attempts to set MADV_DONTFORK on mappings set up for sharing? > > That's my preference as well. If there is a use case for shared or > non-anonymous mappings, then we can implement MADV_DONTFORK with the > semantics for this use case. If we pick some arbitrary semantics > now, > without any use case, we might end up with something that's not > actually > useful. MADV_DONTFORK is existing semantics, and it is enforced on shared, non-anonymous mappings. It is frequently used for things like device mappings, which should not be inherited by a child process, because the device can only be used by one process at a time. When someone requests MADV_DONTFORK on a shared VMA, they will get it. The later madvise request overrides the mmap flags that were used earlier. The question is, should MADV_WIPEONFORK (introduced by this series) have not just different semantics, but also totally different behavior from MADV_DONTFORK? Does the principle of least surprise dictate that the last request determines the policy on an area, or should later requests not be able to override policy that was set at mmap time? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
