Re: [PATCH 1/5] Linux: Add tables with system call numbers

[Florian Weimer <fw@deneb.enyo.de>]

* Siddhesh Poyarekar:

> On 31/12/19 4:52 pm, Florian Weimer wrote:
>>> Prefix the auto-generated files with a comment header like so:
>>>
>>> /* AUTOGENERATED by update-syscall-lists.py. DO NOT EDIT. */
>> 
>> I'm concerned that this unnecessarily makes processing by tools more
>> difficult, so I'd like to avoid this.
>
> The tools only need to filter out \/\*.*\*\/ (or een simpler, omit the
> first line if it's just for these files) which shouldn't be more than a
> line or two of code.  Do you see any other challenges here?  It's a very
> useful comment IMO and definitely worth the extra line of code one would
> have to add to omit comments or even the first line.

I'll see what I can do about this.  It will require quite a bit
re-testing.

>> But we need locking if this is used from build-many-glibcs.py,
>> otherwise we'll lose updates even with the rename approach.  Locking
>> the file being updated is the easiest way to achieve this.  It's true
>> that we have data loss if the script is terminated between the
>> truncate and seek, but most editors have the same issue.  Therefore, I
>> want to leave this as-is.
>
> It would be nice to make build-many-glibcs.py smarter about this.  The
> problem with locking seems limited to syscall-names.list and not
> arch-syscalls.h since the latter ought to be different files for
> build-many-glibcs, right?

No, there are system call tables which are shared across tuples,
e.g. little-endian and big-endian variants.  These also get updated
multiple times.

The only alternative would be to lock a different file, perhaps
sysdeps/unix/sysv/linux/Makefile.  I don't know the impact yet on the
execution time.