NACK/Cmnt: [SRU][J][PATCH 1/2] rcu-tasks: fix mismerge in trc_inspect_reader

[Krister Johansen]

On Fri, Nov 22, 2024 at 11:30:42AM +0100, Stefan Bader wrote:
> On 22.11.24 10:46, Krister Johansen wrote:
> 
> I would in this case change the subject/commit title to:
> 
> [SRU][J][PATCH 1/2] UBUNTU: SAUCE: rcu-tasks: fix mismerge in
> trc_inspect_reader
> 
> BugLink: https://bugs.launchpad.net/bugs/2089373
> 
> > Upstream converted the '!nesting' to 'nesting ? -EINVAL : 0' as part of a manual
> > conflict resolution during their merge of 9b3c4ab304("sched,rcu: Rework
> > try_invoke_on_locked_down_task()").
> > 
> > When this change was pulled into the Ubuntu trees the resulting conflict was
> > incorrectly resolved when the patch was cherry-picked.  Continuing to use
> > '!nesting' results in trc_inspect_reader erroneously flagging tasks as holdouts
> > when they are actually quiescent.  This subsequently results in IPIs being sent
> > to CPUs where one is not needed.  Additionally, on platforms that have CPU
> > hotplug slots empty, this also results in WARNs about errors sending IPIs to
> > invalid CPUs.  Resolving the conflict in the same fashion as linux has addresses
> > this problem.
> > 
> 
> Fixes: 0f17585efd61 "rcu-tasks: Add trc_inspect_reader() checks for exiting
> critical section"
> (backported from commit 6fedc28076bbbb32edb722e80f9406a3d1d668a8)
> > Signed-off-by: Krister Johansen <kjlx at templeofstupid.com>
> 
> That would better show the history of things. The BugLink (note the
> preferred short form also has to be included into each submission. Could you
> re-send this as a new v2 thread?

Yes, apologies for the style gaffe here and thanks for your patience as
I fix this up.  I'll send the requested v2 out shortly.

-K