| Message ID | 20210920135504.1792219-3-nathanl@linux.ibm.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | CPU DLPAR/hotplug for v5.16 | expand |
Le 20/09/2021 à 15:55, Nathan Lynch a écrit : > If, due to bugs elsewhere, we get into unregister_cpu_online() with a CPU > that isn't marked hotpluggable, we can emit a warning and return an > appropriate error instead of crashing. Is it only a bug situation, or is it something that can happen in real life ? If it can happen in real life, kernels with panic_on_warn will still be impacted. > > Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com> > --- > arch/powerpc/kernel/sysfs.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c > index defecb3b1b15..08d8072d6e7a 100644 > --- a/arch/powerpc/kernel/sysfs.c > +++ b/arch/powerpc/kernel/sysfs.c > @@ -928,7 +928,8 @@ static int unregister_cpu_online(unsigned int cpu) > struct device_attribute *attrs, *pmc_attrs; > int i, nattrs; > > - BUG_ON(!c->hotpluggable); > + if (WARN_RATELIMIT(!c->hotpluggable, "cpu %d can't be offlined\n", cpu)) > + return -EBUSY; > > #ifdef CONFIG_PPC64 > if (cpu_has_feature(CPU_FTR_SMT)) >
Christophe Leroy <christophe.leroy@csgroup.eu> writes: > Le 20/09/2021 à 15:55, Nathan Lynch a écrit : >> If, due to bugs elsewhere, we get into unregister_cpu_online() with a CPU >> that isn't marked hotpluggable, we can emit a warning and return an >> appropriate error instead of crashing. > > Is it only a bug situation, or is it something that can happen in real > life ? > > If it can happen in real life, kernels with panic_on_warn will still be > impacted. I only found this by inspection, and it can happen only due to a bug in CPU device registration at boot. The flag must not be set if the platform or CPU can't support going offline.
On 9/20/21 10:55, Nathan Lynch wrote: > If, due to bugs elsewhere, we get into unregister_cpu_online() with a CPU > that isn't marked hotpluggable, we can emit a warning and return an > appropriate error instead of crashing. > > Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com> > --- As mentioned by Christophe this will not solve the crash for kernels with panic_on_warn, but at least it will panic with a clearer message on those and will not panic for everyone else. Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com> > arch/powerpc/kernel/sysfs.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c > index defecb3b1b15..08d8072d6e7a 100644 > --- a/arch/powerpc/kernel/sysfs.c > +++ b/arch/powerpc/kernel/sysfs.c > @@ -928,7 +928,8 @@ static int unregister_cpu_online(unsigned int cpu) > struct device_attribute *attrs, *pmc_attrs; > int i, nattrs; > > - BUG_ON(!c->hotpluggable); > + if (WARN_RATELIMIT(!c->hotpluggable, "cpu %d can't be offlined\n", cpu)) > + return -EBUSY; > > #ifdef CONFIG_PPC64 > if (cpu_has_feature(CPU_FTR_SMT)) >
diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c index defecb3b1b15..08d8072d6e7a 100644 --- a/arch/powerpc/kernel/sysfs.c +++ b/arch/powerpc/kernel/sysfs.c @@ -928,7 +928,8 @@ static int unregister_cpu_online(unsigned int cpu) struct device_attribute *attrs, *pmc_attrs; int i, nattrs; - BUG_ON(!c->hotpluggable); + if (WARN_RATELIMIT(!c->hotpluggable, "cpu %d can't be offlined\n", cpu)) + return -EBUSY; #ifdef CONFIG_PPC64 if (cpu_has_feature(CPU_FTR_SMT))
If, due to bugs elsewhere, we get into unregister_cpu_online() with a CPU that isn't marked hotpluggable, we can emit a warning and return an appropriate error instead of crashing. Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com> --- arch/powerpc/kernel/sysfs.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)