| Message ID | 76ed0b222d2f16fb5aebd144ac0222a7f3b87fa1.camel@marvell.com |
|---|---|
| State | New |
| Headers | show |
| Series | "Task_isolation" mode | expand |
Hi Alex, On Mon, Nov 23, 2020 at 05:58:22PM +0000, Alex Belits wrote: > From: Yuri Norov <ynorov@marvell.com> > > For nohz_full CPUs the desirable behavior is to receive interrupts > generated by tick_nohz_full_kick_cpu(). But for hard isolation it's > obviously not desirable because it breaks isolation. > > This patch adds check for it. > > Signed-off-by: Yuri Norov <ynorov@marvell.com> > [abelits@marvell.com: updated, only exclude CPUs running isolated tasks] > Signed-off-by: Alex Belits <abelits@marvell.com> > --- > kernel/time/tick-sched.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c > index a213952541db..6c8679e200f0 100644 > --- a/kernel/time/tick-sched.c > +++ b/kernel/time/tick-sched.c > @@ -20,6 +20,7 @@ > #include <linux/sched/clock.h> > #include <linux/sched/stat.h> > #include <linux/sched/nohz.h> > +#include <linux/isolation.h> > #include <linux/module.h> > #include <linux/irq_work.h> > #include <linux/posix-timers.h> > @@ -268,7 +269,8 @@ static void tick_nohz_full_kick(void) > */ > void tick_nohz_full_kick_cpu(int cpu) > { > - if (!tick_nohz_full_cpu(cpu)) > + smp_rmb(); > + if (!tick_nohz_full_cpu(cpu) || task_isolation_on_cpu(cpu)) > return; Like I said in subsequent reviews, we are not going to ignore IPIs. We must fix the sources of these IPIs instead. Thanks. > > irq_work_queue_on(&per_cpu(nohz_full_kick_work, cpu), cpu); > -- > 2.20.1 >
On Mon, Nov 23 2020 at 17:58, Alex Belits wrote: > From: Yuri Norov <ynorov@marvell.com> > > For nohz_full CPUs the desirable behavior is to receive interrupts > generated by tick_nohz_full_kick_cpu(). But for hard isolation it's > obviously not desirable because it breaks isolation. > > This patch adds check for it. git grep 'This patch' Documentation/process/ > */ > void tick_nohz_full_kick_cpu(int cpu) > { > - if (!tick_nohz_full_cpu(cpu)) > + smp_rmb(); Undocumented smp_rmb() ... > + if (!tick_nohz_full_cpu(cpu) || task_isolation_on_cpu(cpu)) > return; I still have to see a convincing argument why task isolation is special and not just a straight forward extension of NOHZ full cpu isolation. It's not special as much as you want it to be special. Thanks, tglx
On Mon, Nov 23, 2020 at 05:58:22PM +0000, Alex Belits wrote: > From: Yuri Norov <ynorov@marvell.com> > > For nohz_full CPUs the desirable behavior is to receive interrupts > generated by tick_nohz_full_kick_cpu(). But for hard isolation it's > obviously not desirable because it breaks isolation. > > This patch adds check for it. > > Signed-off-by: Yuri Norov <ynorov@marvell.com> > [abelits@marvell.com: updated, only exclude CPUs running isolated tasks] > Signed-off-by: Alex Belits <abelits@marvell.com> > --- > kernel/time/tick-sched.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c > index a213952541db..6c8679e200f0 100644 > --- a/kernel/time/tick-sched.c > +++ b/kernel/time/tick-sched.c > @@ -20,6 +20,7 @@ > #include <linux/sched/clock.h> > #include <linux/sched/stat.h> > #include <linux/sched/nohz.h> > +#include <linux/isolation.h> > #include <linux/module.h> > #include <linux/irq_work.h> > #include <linux/posix-timers.h> > @@ -268,7 +269,8 @@ static void tick_nohz_full_kick(void) > */ > void tick_nohz_full_kick_cpu(int cpu) > { > - if (!tick_nohz_full_cpu(cpu)) > + smp_rmb(); What does this barrier pair with? The commit message doesn't mention it, and it's not clear in-context. Thanks, Mark. > + if (!tick_nohz_full_cpu(cpu) || task_isolation_on_cpu(cpu)) > return; > > irq_work_queue_on(&per_cpu(nohz_full_kick_work, cpu), cpu); > -- > 2.20.1 >
On Wed, 2020-12-02 at 14:20 +0000, Mark Rutland wrote: > External Email > > ------------------------------------------------------------------- > --- > On Mon, Nov 23, 2020 at 05:58:22PM +0000, Alex Belits wrote: > > From: Yuri Norov <ynorov@marvell.com> > > > > For nohz_full CPUs the desirable behavior is to receive interrupts > > generated by tick_nohz_full_kick_cpu(). But for hard isolation it's > > obviously not desirable because it breaks isolation. > > > > This patch adds check for it. > > > > Signed-off-by: Yuri Norov <ynorov@marvell.com> > > [abelits@marvell.com: updated, only exclude CPUs running isolated > > tasks] > > Signed-off-by: Alex Belits <abelits@marvell.com> > > --- > > kernel/time/tick-sched.c | 4 +++- > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c > > index a213952541db..6c8679e200f0 100644 > > --- a/kernel/time/tick-sched.c > > +++ b/kernel/time/tick-sched.c > > @@ -20,6 +20,7 @@ > > #include <linux/sched/clock.h> > > #include <linux/sched/stat.h> > > #include <linux/sched/nohz.h> > > +#include <linux/isolation.h> > > #include <linux/module.h> > > #include <linux/irq_work.h> > > #include <linux/posix-timers.h> > > @@ -268,7 +269,8 @@ static void tick_nohz_full_kick(void) > > */ > > void tick_nohz_full_kick_cpu(int cpu) > > { > > - if (!tick_nohz_full_cpu(cpu)) > > + smp_rmb(); > > What does this barrier pair with? The commit message doesn't mention > it, > and it's not clear in-context. With barriers in task_isolation_kernel_enter() and task_isolation_exit_to_user_mode(). -- Alex
On Fri, Dec 04, 2020 at 12:54:29AM +0000, Alex Belits wrote: > > On Wed, 2020-12-02 at 14:20 +0000, Mark Rutland wrote: > > External Email > > > > ------------------------------------------------------------------- > > --- > > On Mon, Nov 23, 2020 at 05:58:22PM +0000, Alex Belits wrote: > > > From: Yuri Norov <ynorov@marvell.com> > > > > > > For nohz_full CPUs the desirable behavior is to receive interrupts > > > generated by tick_nohz_full_kick_cpu(). But for hard isolation it's > > > obviously not desirable because it breaks isolation. > > > > > > This patch adds check for it. > > > > > > Signed-off-by: Yuri Norov <ynorov@marvell.com> > > > [abelits@marvell.com: updated, only exclude CPUs running isolated > > > tasks] > > > Signed-off-by: Alex Belits <abelits@marvell.com> > > > --- > > > kernel/time/tick-sched.c | 4 +++- > > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > > > diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c > > > index a213952541db..6c8679e200f0 100644 > > > --- a/kernel/time/tick-sched.c > > > +++ b/kernel/time/tick-sched.c > > > @@ -20,6 +20,7 @@ > > > #include <linux/sched/clock.h> > > > #include <linux/sched/stat.h> > > > #include <linux/sched/nohz.h> > > > +#include <linux/isolation.h> > > > #include <linux/module.h> > > > #include <linux/irq_work.h> > > > #include <linux/posix-timers.h> > > > @@ -268,7 +269,8 @@ static void tick_nohz_full_kick(void) > > > */ > > > void tick_nohz_full_kick_cpu(int cpu) > > > { > > > - if (!tick_nohz_full_cpu(cpu)) > > > + smp_rmb(); > > > > What does this barrier pair with? The commit message doesn't mention > > it, > > and it's not clear in-context. > > With barriers in task_isolation_kernel_enter() > and task_isolation_exit_to_user_mode(). Please add a comment in the code as to what it pairs with. Thanks, Mark.
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index a213952541db..6c8679e200f0 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -20,6 +20,7 @@ #include <linux/sched/clock.h> #include <linux/sched/stat.h> #include <linux/sched/nohz.h> +#include <linux/isolation.h> #include <linux/module.h> #include <linux/irq_work.h> #include <linux/posix-timers.h> @@ -268,7 +269,8 @@ static void tick_nohz_full_kick(void) */ void tick_nohz_full_kick_cpu(int cpu) { - if (!tick_nohz_full_cpu(cpu)) + smp_rmb(); + if (!tick_nohz_full_cpu(cpu) || task_isolation_on_cpu(cpu)) return; irq_work_queue_on(&per_cpu(nohz_full_kick_work, cpu), cpu);