Messages in this thread | | | Date | Wed, 12 Oct 2022 05:55:29 -0700 | From | Yury Norov <> | Subject | Re: [PATCH v2] RISC-V: Fix /proc/cpuinfo cpumask warning |
| |
On Wed, Oct 12, 2022 at 10:29:49AM +0200, Andrew Jones wrote: > Commit 78e5a3399421 ("cpumask: fix checking valid cpu range") has > started issuing warnings[*] when cpu indices equal to nr_cpu_ids - 1 > are passed to cpumask_next* functions. seq_read_iter() and cpuinfo's > start and next seq operations implement a pattern like > > n = cpumask_next(n - 1, mask); > show(n); > while (1) { > ++n; > n = cpumask_next(n - 1, mask); > if (n >= nr_cpu_ids) > break; > show(n); > }
Can you instead of sudo-code print show the real control flow? What function hosts the infinite loop?
> which will issue the warning when reading /proc/cpuinfo. Ensure no > warning is generated by validating the cpu index before calling > cpumask_next(). > > [*] Warnings will only appear with DEBUG_PER_CPU_MAPS enabled. > > Signed-off-by: Andrew Jones <ajones@ventanamicro.com> > Cc: Yury Norov <yury.norov@gmail.com> > --- > v2: > - Got comments on the x86 equivalent patch and made the same > changes to this one > - Added all the information I should have in the first place > to the commit message [Boris] > - Changed style of fix [Boris] > > > arch/riscv/kernel/cpu.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c > index 4aa8cd749441..63138b880b92 100644 > --- a/arch/riscv/kernel/cpu.c > +++ b/arch/riscv/kernel/cpu.c > @@ -166,6 +166,9 @@ static void print_mmu(struct seq_file *f) > > static void *c_start(struct seq_file *m, loff_t *pos) > { > + if (*pos >= nr_cpu_ids) > + return NULL; > + > *pos = cpumask_next(*pos - 1, cpu_online_mask); > if ((*pos) < nr_cpu_ids) > return (void *)(uintptr_t)(1 + *pos);
OK, as far as I understood your explanations, *pos == nr_cpu_ids is a valid index because it's used as stop-code for traversing.
However, you're completely silencing cpumask_check(), including those cases where *pos > nr_cpu_ids. I suspect there's no valid cases for it. If so, the patch should look like:
+ if (*pos == nr_cpu_ids) + return NULL; +
The same for x86 patch.
If it comes to v3, can you send both as a series?
Thanks, Yury
| |