Messages in this thread Patch in this message | | | Date | Wed, 14 Aug 2019 16:58:46 +0800 | From | Ming Lei <> | Subject | Re: [PATCH V3 1/3] genirq/affinity: Enhance warning check |
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On Tue, Aug 13, 2019 at 07:31:39PM +0000, Derrick, Jonathan wrote: > Hi Ming, > > On Tue, 2019-08-13 at 16:14 +0800, Ming Lei wrote: > > The two-stage spread is done on same irq vectors, and we just need that > > either one stage covers all vector, not two stage work together to cover > > all vectors. > > > > So enhance the warning check to make sure all vectors are spread. > > > > Cc: Christoph Hellwig <hch@lst.de> > > Cc: Keith Busch <kbusch@kernel.org> > > Cc: linux-nvme@lists.infradead.org, > > Cc: Jon Derrick <jonathan.derrick@intel.com> > > Cc: Jens Axboe <axboe@kernel.dk> > > Fixes: 6da4b3ab9a6 ("genirq/affinity: Add support for allocating interrupt sets") > > Signed-off-by: Ming Lei <ming.lei@redhat.com> > > --- > > kernel/irq/affinity.c | 3 +-- > > 1 file changed, 1 insertion(+), 2 deletions(-) > > > > diff --git a/kernel/irq/affinity.c b/kernel/irq/affinity.c > > index 6fef48033f96..265b3076f16b 100644 > > --- a/kernel/irq/affinity.c > > +++ b/kernel/irq/affinity.c > > @@ -215,8 +215,7 @@ static int irq_build_affinity_masks(unsigned int startvec, unsigned int numvecs, > > npresmsk, nmsk, masks); > > put_online_cpus(); > > > > - if (nr_present < numvecs) > > - WARN_ON(nr_present + nr_others < numvecs); > > + WARN_ON(max(nr_present, nr_others) < numvecs); > > I think the patch description assumes the first condition > "The two-stage spread is done on same irq vectors" > > /* > * Spread on non present CPUs starting from the next vector to be > * handled. If the spreading of present CPUs already exhausted the > * vector space, assign the non present CPUs to the already spread > * out vectors. > */ > if (nr_present >= numvecs) > curvec = firstvec; > > But doesn't following condition imply nr_others spread is potentionally > different vector set? > > else > curvec = firstvec + nr_present; >
Most times, __irq_build_affinity_masks() returns numvecs.
However, each stage may expose less CPU number than num_vecs, then less vectors than 'numvecs' can be spread.
So this patch is actually wrong.
Thank, Ming
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