modules/kmod: replace implementation with a semaphore
authorLuis Chamberlain <mcgrof@kernel.org>
Sat, 25 Mar 2023 01:38:00 +0000 (18:38 -0700)
committerLuis Chamberlain <mcgrof@kernel.org>
Tue, 18 Apr 2023 18:15:24 +0000 (11:15 -0700)
commit25a1b5b518f4336bff934ac8348da6c57158363a
treefcdef84da3cc37fb0459582ced035f522adb1bd7
parent48380368dec14859723b9e3fbd43e042638d9a76
modules/kmod: replace implementation with a semaphore

Simplify the concurrency delimiter we use for kmod with the semaphore.
I had used the kmod strategy to try to implement a similar concurrency
delimiter for the kernel_read*() calls from the finit_module() path
so to reduce vmalloc() memory pressure. That effort didn't provide yet
conclusive results, but one thing that became clear is we can use
the suggested alternative solution with semaphores which Linus hinted
at instead of using the atomic / wait strategy.

I've stress tested this with kmod test 0008:

time /data/linux-next/tools/testing/selftests/kmod/kmod.sh -t 0008

And I get only a *slight* delay. That delay however is small, a few
seconds for a full test loop run that runs 150 times, for about ~30-40
seconds. The small delay is worth the simplfication IMHO.

Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
kernel/module/kmod.c