| Message ID | 20221012082949.1801222-1-ajones@ventanamicro.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | [v2] RISC-V: Fix /proc/cpuinfo cpumask warning | expand |
On Wed, Oct 12, 2022 at 1:59 PM Andrew Jones <ajones@ventanamicro.com> 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); > } > > 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> Looks good to me. Reviewed-by: Anup Patel <anup@brainfault.org> Regards, Anup > --- > 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); > -- > 2.37.3 >
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); > } > > 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> Reviewed-by: Conor Dooley <conor.dooley@microchip.com> Tested-by: Conor Dooley <conor.dooley@microchip.com> Thanks > --- > 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); > -- > 2.37.3 >
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
On Wed, Oct 12, 2022 at 05:55:29AM -0700, Yury Norov wrote: > 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? The function is seq_read_iter(), which is pointed out above. I'd rather not reproduce / describe more than what I've done here, as the function is large. I'd be happy for reviewers to double check my pseudocode to make sure I got it and the analysis right, though. > > > 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; > + That makes sense and it's probably worth a v3. I'll wait and see if more comments roll in before sending though. > > The same for x86 patch. > > If it comes to v3, can you send both as a series? OK. I'll write a cover letter trying to explain that I don't expect them to both go through the same tree. Thanks, drew
On Wed, Oct 12, 2022 at 6:13 AM Andrew Jones <ajones@ventanamicro.com> wrote: > > On Wed, Oct 12, 2022 at 05:55:29AM -0700, Yury Norov wrote: > > 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? > > The function is seq_read_iter(), which is pointed out above. I'd rather > not reproduce / describe more than what I've done here, as the function > is large. I'd be happy for reviewers to double check my pseudocode to > make sure I got it and the analysis right, though. > > > > > > 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; > > + > > That makes sense and it's probably worth a v3. I'll wait and see if more > comments roll in before sending though. > > > > > The same for x86 patch. > > > > If it comes to v3, can you send both as a series? > > OK. I'll write a cover letter trying to explain that I don't expect them > to both go through the same tree. I can take it in my tree, if it helps.
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);
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); } 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(+)