linux-kernel - Re: [PATCH v2 2/2] module: Merge same-name module load requests

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Date:   Tue, 22 Nov 2022 14:59:18 +0100
From:   Petr Pavlu <petr.pavlu@...e.com>
To:     Luis Chamberlain <mcgrof@...nel.org>
Cc:     Prarit Bhargava <prarit@...hat.com>, pmladek@...e.com,
        linux-modules@...r.kernel.org, linux-kernel@...r.kernel.org,
        David Hildenbrand <david@...hat.com>
Subject: Re: [PATCH v2 2/2] module: Merge same-name module load requests

On 11/21/22 20:03, Luis Chamberlain wrote:
> To be clear I don't care about the patch mentioned in the above URL, I care
> about this:
> 
> https://lkml.kernel.org/r/d0bc50e3-0e42-311b-20ed-7538bb918c5b@suse.com
> [...]
> 
> Petr, you had mentioned in the commit log for your second patch in this
> thread that your change fixes a regression. What I asked for was for a
> patch that fixes that regression alone first so we can send to stable.
> So what issue is that alternative patch fixing?

This alternative patch fixes the discussed regression with failing inserts of
acpi_cpufreq and pcc_cpufreq delaying boot. As mentioned, the situation can in
the worst case prevent udev from loading drivers for other devices and might
cause timeouts of services waiting on them and subsequently a failed boot.

The patch attempts a different solution for the problem that 6e6de3dee51a was
trying to solve. Rather than waiting for the unloading to complete, it returns
a different error code (-EBUSY) for modules in the GOING state. This should
avoid the error situation that was described in 6e6de3dee51a (user space
attempting to load a dependent module because the -EEXIST error code would
suggest to user space that the first module had been loaded successfully),
while avoiding the delay issue too.

Petr