On Tue, Jul 21, 2020 at 03:50:35PM -0700, Palmer Dabbelt wrote: > On Mon, 20 Jul 2020 12:14:03 PDT (-0700), Greg KH wrote: > > On Mon, Jul 20, 2020 at 06:50:10PM +0000, Atish Patra wrote: > > > On Mon, 2020-07-20 at 23:11 +0530, Naresh Kamboju wrote: > > > > RISC-V build breaks on stable-rc 5.7 branch. > > > > build failed with gcc-8, gcc-9 and gcc-9. > > > > > > > > > > Sorry for the compilation issue. > > > > > > mmap_read_lock was intrdouced in the following commit. > > > > > > commit 9740ca4e95b4 > > > Author: Michel Lespinasse <walken@xxxxxxxxxx> > > > Date: Mon Jun 8 21:33:14 2020 -0700 > > > > > > mmap locking API: initial implementation as rwsem wrappers > > > > > > The following two commits replaced the usage of mmap_sem rwsem calls > > > with mmap_lock. > > > > > > d8ed45c5dcd4 (mmap locking API: use coccinelle to convert mmap_sem > > > rwsem call sites) > > > 89154dd5313f (mmap locking API: convert mmap_sem call sites missed by > > > coccinelle) > > > > > > The first commit is not present in stale 5.7-y for obvious reasons. > > > > > > Do we need to send a separate patch only for stable branch with > > > mmap_sem ? I am not sure if that will cause a conflict again in future. > > > > I do not like taking odd backports, and would rather take the real patch > > that is upstream. > > I guess I'm a bit new to stable backports so I'm not sure what's expected here. > The failing patch fixes a bug by using a new interface. The smallest diff fix > for the stable kernels would be to construct a similar fix without the new > interface, which in this case is very easy as the new interface just converted > some generic locking calls to one-line functions. It seems somewhat circuitous > to land that in Linus' tree, though, as it would require breaking our port > before fixing it to use the old interfaces and then cleaning it up to use the > new interfaces. > > Are we expected to pull the new interface onto stable in addition to this fix? If it really does fix a big issue, yes, that is fine to do. > The new interface doesn't actually fix anything itself, but it would allow a > functional kernel to be constructed that consisted of only backports from > Linus' tree (which would also make further fixes easier). That's fine. > It seems safe to > just pull in 9740ca4e95b4 ("mmap locking API: initial implementation as rwsem > wrappers") before this failing patch, as in this case the new interface will > function correctly with only a subset of callers having been converted. Of > course that's not a generally true statement so I don't know if future code > will behave that way, but pulling in those conversion patches is definitely > unnecessary diff right now. If someone wants to send me a full set of the git ids that need to be pulled in, I will be glad to do so. thanks, greg k-h