tree c50d7448e058e1e8f47d7fd04986ab3a9a186ae4
parent 4c123de90e479dcd750916a258cb0a3108def241
author Luis R. Rodriguez <mcgrof@kernel.org> 1481865862 -0600
committer Luis R. Rodriguez <mcgrof@kernel.org> 1495832541 -0700

kmod: throttle kmod thread limit

If we reach the limit of modprobe_limit threads running the next
request_module() call will fail. The original reason for adding
a kill was to do away with possible issues with in old circumstances
which would create a recursive series of request_module() calls.
We can do better than just be super aggressive and reject calls
once we've reached the limit by simply making pending callers wait
until the threshold has been reduced.

The only difference is the clutch helps with avoiding making
request_module() requests fatal more often. With x86_64 qemu,
with 4 cores, 4 GiB of RAM it takes the following run time to
run both tests:

time ./kmod.sh -t 0008
real    0m12.364s
user    0m0.704s
sys     0m5.373s

time ./kmod.sh -t 0009
real    0m47.638s
user    0m1.033s
sys     0m5.425s

Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>