tree 5b84043b800db520f551c86f10418e2e2a852cf0
parent 6f13909f4fe9652f189b462c6c98767309000321
author Rusty Russell <rusty@rustcorp.com.au> 1348808463 +0930
committer Rusty Russell <rusty@rustcorp.com.au> 1348808463 +0930

module: wait when loading a module which is currently initializing.

The original module-init-tools module loader used a fnctl lock on the
.ko file to avoid attempts to simultaneously load a module.
Unfortunately, you can't get an exclusive fcntl lock on a read-only
fd, making this not work for read-only mounted filesystems.
module-init-tools has a hacky sleep-and-loop for this now.

It's not that hard to wait in the kernel, and only return -EEXIST once
the first module has finished loading (or continue loading the module
if the first one failed to initialize for some reason).  It's also
consistent with what we do for dependent modules which are still loading.

Suggested-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>