| Message ID | 1397762146-8337-4-git-send-email-ashwin.chaugule@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, Apr 17, 2014 at 08:15:46PM +0100, Ashwin Chaugule wrote: > PSCIv0.2 adds a new function called AFFINITY_INFO, which > can be used to query if a specified CPU has actually gone > offline. Calling this function via cpu_kill ensures that > a CPU has quiesced after a call to cpu_die. > > Signed-off-by: Ashwin Chaugule <ashwin.chaugule@linaro.org> > Reviewed-by: Rob Herring <robh@kernel.org> > --- > arch/arm/kernel/psci_smp.c | 21 +++++++++++++++++++++ > include/uapi/linux/psci.h | 5 +++++ > 2 files changed, 26 insertions(+) > > diff --git a/arch/arm/kernel/psci_smp.c b/arch/arm/kernel/psci_smp.c > index 570a48c..c6f1420 100644 > --- a/arch/arm/kernel/psci_smp.c > +++ b/arch/arm/kernel/psci_smp.c > @@ -16,6 +16,7 @@ > #include <linux/init.h> > #include <linux/smp.h> > #include <linux/of.h> > +#include <uapi/linux/psci.h> > > #include <asm/psci.h> > #include <asm/smp_plat.h> > @@ -66,6 +67,25 @@ void __ref psci_cpu_die(unsigned int cpu) > /* We should never return */ > panic("psci: cpu %d failed to shutdown\n", cpu); > } > + > +int __ref psci_cpu_kill(unsigned int cpu) > +{ > + int err; > + > + if (!psci_ops.affinity_info) > + return 1; > + > + err = psci_ops.affinity_info(cpu_logical_map(cpu), 0); > + > + if (err != PSCI_AFFINITY_INFO_RET_OFF) { > + pr_err("psci: Cannot kill CPU:%d, psci ret val: %d\n", > + cpu, err); > + /* Make platform_cpu_kill() fail. */ > + return 0; > + } We can race with the dying CPU here -- if we call AFFINITY_INFO before the dying cpu is sufficiently far through its CPU_OFF call it won't register as OFF. Could we poll here instead (with a reasonable limit on the number of iterations)? That would enable us to not spuriously declare a CPU to be dead when it happened to take slightly longer than we expect to turn off. Otherwise, this looks good. Thanks for implementing this :) Cheers, Mark.
Hi Mark, On 17 April 2014 15:50, Mark Rutland <mark.rutland@arm.com> wrote: > On Thu, Apr 17, 2014 at 08:15:46PM +0100, Ashwin Chaugule wrote: >> PSCIv0.2 adds a new function called AFFINITY_INFO, which >> can be used to query if a specified CPU has actually gone >> offline. Calling this function via cpu_kill ensures that >> a CPU has quiesced after a call to cpu_die. >> >> Signed-off-by: Ashwin Chaugule <ashwin.chaugule@linaro.org> >> Reviewed-by: Rob Herring <robh@kernel.org> >> --- >> arch/arm/kernel/psci_smp.c | 21 +++++++++++++++++++++ >> include/uapi/linux/psci.h | 5 +++++ >> 2 files changed, 26 insertions(+) >> >> diff --git a/arch/arm/kernel/psci_smp.c b/arch/arm/kernel/psci_smp.c >> index 570a48c..c6f1420 100644 >> --- a/arch/arm/kernel/psci_smp.c >> +++ b/arch/arm/kernel/psci_smp.c >> @@ -16,6 +16,7 @@ >> #include <linux/init.h> >> #include <linux/smp.h> >> #include <linux/of.h> >> +#include <uapi/linux/psci.h> >> >> #include <asm/psci.h> >> #include <asm/smp_plat.h> >> @@ -66,6 +67,25 @@ void __ref psci_cpu_die(unsigned int cpu) >> /* We should never return */ >> panic("psci: cpu %d failed to shutdown\n", cpu); >> } >> + >> +int __ref psci_cpu_kill(unsigned int cpu) >> +{ >> + int err; >> + >> + if (!psci_ops.affinity_info) >> + return 1; >> + >> + err = psci_ops.affinity_info(cpu_logical_map(cpu), 0); >> + >> + if (err != PSCI_AFFINITY_INFO_RET_OFF) { >> + pr_err("psci: Cannot kill CPU:%d, psci ret val: %d\n", >> + cpu, err); >> + /* Make platform_cpu_kill() fail. */ >> + return 0; >> + } > > We can race with the dying CPU here -- if we call AFFINITY_INFO before > the dying cpu is sufficiently far through its CPU_OFF call it won't > register as OFF. > > Could we poll here instead (with a reasonable limit on the number of > iterations)? That would enable us to not spuriously declare a CPU to be > dead when it happened to take slightly longer than we expect to turn > off. True. How about something like this? int __ref psci_cpu_kill(unsigned int cpu) { - int err; + int err, retries; if (!psci_ops.affinity_info) return 1; - + /* + * cpu_kill could race with cpu_die and we can + * potentially end up declaring this cpu undead + * while it is dying. So retry a couple of times. + */ +retry: err = psci_ops.affinity_info(cpu_logical_map(cpu), 0); if (err != PSCI_AFFINITY_INFO_RET_OFF) { + if (++retries < 3) { + pr_info("Retrying check for CPU kill: %d\n", retries); + goto retry; + } pr_err("psci: Cannot kill CPU:%d, psci ret val: %d\n", cpu, err); /* Make platform_cpu_kill() fail. */ Cheers, Ashwin
On 18 April 2014 11:21, Ashwin Chaugule <ashwin.chaugule@linaro.org> wrote: > Hi Mark, > > > On 17 April 2014 15:50, Mark Rutland <mark.rutland@arm.com> wrote: >> On Thu, Apr 17, 2014 at 08:15:46PM +0100, Ashwin Chaugule wrote: >>> PSCIv0.2 adds a new function called AFFINITY_INFO, which >>> can be used to query if a specified CPU has actually gone >>> offline. Calling this function via cpu_kill ensures that >>> a CPU has quiesced after a call to cpu_die. >>> >>> Signed-off-by: Ashwin Chaugule <ashwin.chaugule@linaro.org> >>> Reviewed-by: Rob Herring <robh@kernel.org> >>> --- >>> arch/arm/kernel/psci_smp.c | 21 +++++++++++++++++++++ >>> include/uapi/linux/psci.h | 5 +++++ >>> 2 files changed, 26 insertions(+) >>> >>> diff --git a/arch/arm/kernel/psci_smp.c b/arch/arm/kernel/psci_smp.c >>> index 570a48c..c6f1420 100644 >>> --- a/arch/arm/kernel/psci_smp.c >>> +++ b/arch/arm/kernel/psci_smp.c >>> @@ -16,6 +16,7 @@ >>> #include <linux/init.h> >>> #include <linux/smp.h> >>> #include <linux/of.h> >>> +#include <uapi/linux/psci.h> >>> >>> #include <asm/psci.h> >>> #include <asm/smp_plat.h> >>> @@ -66,6 +67,25 @@ void __ref psci_cpu_die(unsigned int cpu) >>> /* We should never return */ >>> panic("psci: cpu %d failed to shutdown\n", cpu); >>> } >>> + >>> +int __ref psci_cpu_kill(unsigned int cpu) >>> +{ >>> + int err; >>> + >>> + if (!psci_ops.affinity_info) >>> + return 1; >>> + >>> + err = psci_ops.affinity_info(cpu_logical_map(cpu), 0); >>> + >>> + if (err != PSCI_AFFINITY_INFO_RET_OFF) { >>> + pr_err("psci: Cannot kill CPU:%d, psci ret val: %d\n", >>> + cpu, err); >>> + /* Make platform_cpu_kill() fail. */ >>> + return 0; >>> + } >> >> We can race with the dying CPU here -- if we call AFFINITY_INFO before >> the dying cpu is sufficiently far through its CPU_OFF call it won't >> register as OFF. >> >> Could we poll here instead (with a reasonable limit on the number of >> iterations)? That would enable us to not spuriously declare a CPU to be >> dead when it happened to take slightly longer than we expect to turn >> off. > > True. How about something like this? > > int __ref psci_cpu_kill(unsigned int cpu) > { > - int err; > + int err, retries; > > if (!psci_ops.affinity_info) > return 1; > - > + /* > + * cpu_kill could race with cpu_die and we can > + * potentially end up declaring this cpu undead > + * while it is dying. So retry a couple of times. > + */ > +retry: > err = psci_ops.affinity_info(cpu_logical_map(cpu), 0); > > if (err != PSCI_AFFINITY_INFO_RET_OFF) { > + if (++retries < 3) { > + pr_info("Retrying check for CPU kill: %d\n", retries); > + goto retry; > + } > pr_err("psci: Cannot kill CPU:%d, psci ret val: %d\n", > cpu, err); > /* Make platform_cpu_kill() fail. */ > > > Hi Rob, I've already got your Reviewed-by on this patch without this "retry" thing. Are you okay with this as well? I can then roll it up in one patch. Cheers, Ashwin
On Thu, Apr 24, 2014 at 9:33 AM, Ashwin Chaugule <ashwin.chaugule@linaro.org> wrote: > On 18 April 2014 11:21, Ashwin Chaugule <ashwin.chaugule@linaro.org> wrote: >> Hi Mark, >> >> >> On 17 April 2014 15:50, Mark Rutland <mark.rutland@arm.com> wrote: >>> On Thu, Apr 17, 2014 at 08:15:46PM +0100, Ashwin Chaugule wrote: >>>> PSCIv0.2 adds a new function called AFFINITY_INFO, which >>>> can be used to query if a specified CPU has actually gone >>>> offline. Calling this function via cpu_kill ensures that >>>> a CPU has quiesced after a call to cpu_die. [...] >>> We can race with the dying CPU here -- if we call AFFINITY_INFO before >>> the dying cpu is sufficiently far through its CPU_OFF call it won't >>> register as OFF. >>> >>> Could we poll here instead (with a reasonable limit on the number of >>> iterations)? That would enable us to not spuriously declare a CPU to be >>> dead when it happened to take slightly longer than we expect to turn >>> off. >> >> True. How about something like this? >> >> int __ref psci_cpu_kill(unsigned int cpu) >> { >> - int err; >> + int err, retries; >> >> if (!psci_ops.affinity_info) >> return 1; >> - >> + /* >> + * cpu_kill could race with cpu_die and we can >> + * potentially end up declaring this cpu undead >> + * while it is dying. So retry a couple of times. >> + */ >> +retry: >> err = psci_ops.affinity_info(cpu_logical_map(cpu), 0); >> >> if (err != PSCI_AFFINITY_INFO_RET_OFF) { >> + if (++retries < 3) { >> + pr_info("Retrying check for CPU kill: %d\n", retries); >> + goto retry; >> + } >> pr_err("psci: Cannot kill CPU:%d, psci ret val: %d\n", >> cpu, err); >> /* Make platform_cpu_kill() fail. */ >> >> >> > > > Hi Rob, I've already got your Reviewed-by on this patch without this > "retry" thing. Are you okay with this as well? I can then roll it up > in one patch. Yes. My only comment is I would perhaps add a sleep (or delay if this context cannot sleep) on the retry. I'm not sure what I reasonable time would be, but at least then you are waiting a defined amount of time versus how long it takes this code to execute. Rob
diff --git a/arch/arm/kernel/psci_smp.c b/arch/arm/kernel/psci_smp.c index 570a48c..c6f1420 100644 --- a/arch/arm/kernel/psci_smp.c +++ b/arch/arm/kernel/psci_smp.c @@ -16,6 +16,7 @@ #include <linux/init.h> #include <linux/smp.h> #include <linux/of.h> +#include <uapi/linux/psci.h> #include <asm/psci.h> #include <asm/smp_plat.h> @@ -66,6 +67,25 @@ void __ref psci_cpu_die(unsigned int cpu) /* We should never return */ panic("psci: cpu %d failed to shutdown\n", cpu); } + +int __ref psci_cpu_kill(unsigned int cpu) +{ + int err; + + if (!psci_ops.affinity_info) + return 1; + + err = psci_ops.affinity_info(cpu_logical_map(cpu), 0); + + if (err != PSCI_AFFINITY_INFO_RET_OFF) { + pr_err("psci: Cannot kill CPU:%d, psci ret val: %d\n", + cpu, err); + /* Make platform_cpu_kill() fail. */ + return 0; + } + return 1; +} + #endif bool __init psci_smp_available(void) @@ -78,5 +98,6 @@ struct smp_operations __initdata psci_smp_ops = { .smp_boot_secondary = psci_boot_secondary, #ifdef CONFIG_HOTPLUG_CPU .cpu_die = psci_cpu_die, + .cpu_kill = psci_cpu_kill, #endif }; diff --git a/include/uapi/linux/psci.h b/include/uapi/linux/psci.h index a4136c3..857209b 100644 --- a/include/uapi/linux/psci.h +++ b/include/uapi/linux/psci.h @@ -74,4 +74,9 @@ #define PSCI_RET_NOT_PRESENT -7 #define PSCI_RET_DISABLED -8 +/* Return values from the PSCI_ID_AFFINITY_INFO Function. */ +#define PSCI_AFFINITY_INFO_RET_ON 0 +#define PSCI_AFFINITY_INFO_RET_OFF 1 +#define PSCI_AFFINITY_INFO_RET_ON_PENDING 2 + #endif /* _UAPI_LINUX_PSCI_H */