Messages in this thread | | | From | John Ogness <> | Subject | Re: [PATCH printk v2 3/4] printk: Skip unfinalized records in panic | Date | Wed, 18 Oct 2023 17:56:52 +0206 |
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On 2023-10-18, Petr Mladek <pmladek@suse.com> wrote: > So it is the _last_ finalized id from the timing POV. If there are > more CPUs storing and finalizing the messages in parallel then > it might change forth and back. There might be earlier non-finalized > records and newer finalized ones. > > It means that prb_next_seq() really is the best effort and > the description is not valid:
Well, the description was valid until prb_next_seq() was optimized and converted to best-effort with:
commit f244b4dc53e5 ("printk: ringbuffer: Improve prb_next_seq() performance")
> It would be great to document these subtle details especially when > we are going to depend on them.
Going through the various call sites of prb_next_seq(), I would argue that the above optimization introduced some bugs. I will investigate if prb_next_seq() can be fixed to match its description because the current users already depend on that.
WRT to this series, I have put together an alternative implementation that does not use prb_next_seq().
John
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