Re: [PATCH iptables] xshared: Implement xtables lock timeout using signals

[Florian Westphal <fw@strlen.de>]

Jethro Beekman <jethro@fortanix.com> wrote:
> Previously, if a lock timeout is specified using `-w`, flock() is called
> using LOCK_NB in a loop with a sleep. This results in two issues.
>
> The first issue is that the process may wait longer than necessary when
> the lock becomes available. For this the `-W` option was added, but this
> requires fine-tuning.
> 
> The second issue is that if lock contention is high, invocations using
> `-w` without a timeout will always win lock acquisition from
> invocations that use `-w` *with* a timeout. This is because invocations
> using `-w` are actively waiting on the lock whereas the others only
> check from time to time whether the lock is free, which will never be
> the case.
> 
> This patch removes the `-W` option and the sleep loop. Instead, flock()
> is always called in a blocking fashion, but the alarm() function is used
> with a non-SA_RESTART signal handler to cancel the system call.

Doesn't apply anymore, if you send a rebased version I'll apply it.