Messages in this thread | | | Date | Fri, 31 Jul 2020 15:19:38 +0530 | From | Srikar Dronamraju <> | Subject | Re: [PATCH v4 08/10] powerpc/smp: Allocate cpumask only after searching thread group |
| |
* Michael Ellerman <mpe@ellerman.id.au> [2020-07-31 17:52:15]:
> Srikar Dronamraju <srikar@linux.vnet.ibm.com> writes: > > If allocated earlier and the search fails, then cpumask need to be > > freed. However cpu_l1_cache_map can be allocated after we search thread > > group. > > It's not freed anywhere AFAICS? >
Yes, its never freed. Infact we are never checking if zalloc_cpumask_var_node fails. Its not just this cpumask, but historically all the other existing cpumasks in arch/powerpc/kernel/smp.c are never freed/checked. I did dig into this a bit and it appears that .. (Please do correct me if I am wrong!! )
Powerpc using cpumask_var_t for all of the percpu variables. And it dont seem to enable CONFIG_CPUMASK_OFFSTACK even from the MAXSMP config.
So from include/linux/cpumask.h
typedef struct cpumask cpumask_var_t[1]; and zalloc_cpumask_var_node ends up being cpumask_clear
So I think we are historically we seem to assume we are always !CPUMASK_OFFSTACK and hence we dont need to check for return as well as free..
I would look forward to your comments on how we should handle this going forward. But I would keep this the same for this patchset.
One of the questions that I have is if we most likely are to be in !CONFIG_CPUMASK_OFFSTACK, then should be migrate to cpumask_t for percpu variables.
The reason being we end up using NR_CPU cpumask for each percpu cpumask variable instead of using NR_CPU cpumask_t pointer.
> And even after this change there's still an error path that doesn't free > it, isn't there? > > cheers > > > Cc: linuxppc-dev <linuxppc-dev@lists.ozlabs.org> > > Cc: LKML <linux-kernel@vger.kernel.org> > > Cc: Michael Ellerman <mpe@ellerman.id.au> > > Cc: Nicholas Piggin <npiggin@gmail.com> > > Cc: Anton Blanchard <anton@ozlabs.org> > > Cc: Oliver O'Halloran <oohall@gmail.com> > > Cc: Nathan Lynch <nathanl@linux.ibm.com> > > Cc: Michael Neuling <mikey@neuling.org> > > Cc: Gautham R Shenoy <ego@linux.vnet.ibm.com> > > Cc: Ingo Molnar <mingo@kernel.org> > > Cc: Peter Zijlstra <peterz@infradead.org> > > Cc: Valentin Schneider <valentin.schneider@arm.com> > > Cc: Jordan Niethe <jniethe5@gmail.com> > > Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com> > > Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> > > --- > > arch/powerpc/kernel/smp.c | 7 +++---- > > 1 file changed, 3 insertions(+), 4 deletions(-) > > > > diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c > > index 698000c7f76f..dab96a1203ec 100644 > > --- a/arch/powerpc/kernel/smp.c > > +++ b/arch/powerpc/kernel/smp.c > > @@ -797,10 +797,6 @@ static int init_cpu_l1_cache_map(int cpu) > > if (err) > > goto out; > > > > - zalloc_cpumask_var_node(&per_cpu(cpu_l1_cache_map, cpu), > > - GFP_KERNEL, > > - cpu_to_node(cpu)); > > - > > cpu_group_start = get_cpu_thread_group_start(cpu, &tg); > > > > if (unlikely(cpu_group_start == -1)) { > > @@ -809,6 +805,9 @@ static int init_cpu_l1_cache_map(int cpu) > > goto out; > > } > > > > + zalloc_cpumask_var_node(&per_cpu(cpu_l1_cache_map, cpu), > > + GFP_KERNEL, cpu_to_node(cpu)); > > + > > for (i = first_thread; i < first_thread + threads_per_core; i++) { > > int i_group_start = get_cpu_thread_group_start(i, &tg); > > > > -- > > 2.17.1
-- Thanks and Regards Srikar Dronamraju
| |