On Sun, Apr 25, 2021 at 9:59 PM Naresh Kamboju <naresh.kamboju@xxxxxxxxxx> wrote: > > Hi Eric, > > On Fri, 16 Apr 2021 at 23:27, Jakub Kicinski <kuba@xxxxxxxxxx> wrote: > > > > On Thu, 15 Apr 2021 10:37:53 -0700 Eric Dumazet wrote: > > > From: Eric Dumazet <edumazet@xxxxxxxxxx> > > > > > > Calling two copy_to_user() for very small regions has very high overhead. > > > > > > Switch to inlined unsafe_put_user() to save one stac/clac sequence, > > > and avoid copy_to_user(). > > > > > > Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx> > > > Cc: Soheil Hassas Yeganeh <soheil@xxxxxxxxxx> > > > > Hi Eric! > > > > This appears to break boot on my systems. > > I have been noticing this problem. > > > > > IDK how exactly, looks like systemd gets stuck waiting for nondescript > > services to start in initramfs. I have lots of debug enabled and didn't > > spot anything of note in kernel logs. > > We (LKFT) are still seeing this problem only on arm architecture on > next-20210416 tag onwards. our bisect script points to this commit. > > Steps to reproduce: > - build linux next latest next-20210423 tag with below config > - kernel-config: > https://builds.tuxbuild.com/1reqrnNLnHEX9uEZFngRfaoJa9E/config > - boot qemu-arm with below command > - /usr/bin/qemu-system-aarch64 -cpu host,aarch64=off -machine > virt-2.10,accel=kvm -nographic -net > nic,model=virtio,macaddr=BA:DD:AD:CC:09:04 -net tap -m 2048 -monitor > none -kernel zImage --append "console=ttyAMA0 root=/dev/vda rw" -hda > rpb-console-image-lkft-am57xx-evm-20201022181203-3085.rootfs.ext4 -m > 4096 -smp 2 -nographic > > - After the mount rootfs - the systemd gets stuck > > > > > I'll try to poke at this more, but LMK if you have any ideas. The > > commit looks "obviously correct" :S > > May I request to investigate this on arm architecture. > The qemu_arm boot failed link, > https://lkft.validation.linaro.org/scheduler/job/2565371#L540 > > The qemu_arm boot pass after the reverting this patch, > commit 38ebcf5096a86762b82262e96b2c8b170fe79040 > scm: optimize put_cmsg() Well, as already reported, this patch had an obvious typo. Fixed later by "scm: fix a typo in put_cmsg()" Can you trace put_cmsg() and check that systemd passes an aligned control buffer ? Kernel was indeed able to handle arbitrary alignment, but why the application would force slow copyout() (alignment mismatch between source/destination buffers) is quite strange. > > on the latest linux next tags i have to revert two commits. > "scm: fix a typo in put_cmsg()" > "scm: optimize put_cmsg()" > > Reported-by: Naresh Kamboju <naresh.kamboju@xxxxxxxxxx> > > -- > Linaro LKFT > https://lkft.linaro.org
