Messages in this thread | | | Date | Mon, 22 Aug 2022 07:15:45 -0700 | From | Yury Norov <> | Subject | Re: [RFC 07/10] lib/cpumask: Introduce cpumask_not_dying_but() |
| |
On Mon, Aug 22, 2022 at 10:15:17AM +0800, Pingfan Liu wrote: > During cpu hot-removing, the dying cpus are still in cpu_online_mask. > On the other hand, A subsystem will migrate its broker from the dying > cpu to a online cpu in its teardown cpuhp_step. > > After enabling the teardown of cpus in parallel, cpu_online_mask can not > tell those dying from the real online. > > Introducing a function cpumask_not_dying_but() to pick a real online > cpu. > > Signed-off-by: Pingfan Liu <kernelfans@gmail.com> > Cc: Yury Norov <yury.norov@gmail.com> > Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> > Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Steven Price <steven.price@arm.com> > Cc: Mark Rutland <mark.rutland@arm.com> > Cc: "Jason A. Donenfeld" <Jason@zx2c4.com> > Cc: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com> > To: linux-kernel@vger.kernel.org > --- > include/linux/cpumask.h | 3 +++ > kernel/cpu.c | 3 +++ > lib/cpumask.c | 18 ++++++++++++++++++ > 3 files changed, 24 insertions(+) > > diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h > index 0d435d0edbcb..d2033a239a07 100644 > --- a/include/linux/cpumask.h > +++ b/include/linux/cpumask.h > @@ -317,6 +317,9 @@ unsigned int cpumask_any_but(const struct cpumask *mask, unsigned int cpu) > return i; > } > > +/* for parallel kexec reboot */ > +int cpumask_not_dying_but(const struct cpumask *mask, unsigned int cpu); > + > #define CPU_BITS_NONE \ > { \ > [0 ... BITS_TO_LONGS(NR_CPUS)-1] = 0UL \ > diff --git a/kernel/cpu.c b/kernel/cpu.c > index 90debbe28e85..771e344f8ff9 100644 > --- a/kernel/cpu.c > +++ b/kernel/cpu.c > @@ -1282,6 +1282,9 @@ static void cpus_down_no_rollback(struct cpumask *cpus) > struct cpuhp_cpu_state *st; > unsigned int cpu; > > + for_each_cpu(cpu, cpus) > + set_cpu_dying(cpu, true); > + > /* launch ap work one by one, but not wait for completion */ > for_each_cpu(cpu, cpus) { > st = per_cpu_ptr(&cpuhp_state, cpu); > diff --git a/lib/cpumask.c b/lib/cpumask.c > index 8baeb37e23d3..6474f07ed87a 100644 > --- a/lib/cpumask.c > +++ b/lib/cpumask.c > @@ -7,6 +7,24 @@ > #include <linux/memblock.h> > #include <linux/numa.h> > > +/* Used in parallel kexec-reboot cpuhp callbacks */ > +int cpumask_not_dying_but(const struct cpumask *mask, > + unsigned int cpu) > +{ > + unsigned int i; > + > + if (CONFIG_SHUTDOWN_NONBOOT_CPUS) {
Hmm... Would it even work? Anyways, the documentation says: Within code, where possible, use the IS_ENABLED macro to convert a Kconfig symbol into a C boolean expression, and use it in a normal C conditional:
.. code-block:: c
if (IS_ENABLED(CONFIG_SOMETHING)) { ... }
> + cpumask_check(cpu); > + for_each_cpu(i, mask) > + if (i != cpu && !cpumask_test_cpu(i, cpu_dying_mask)) > + break; > + return i; > + } else { > + return cpumask_any_but(mask, cpu); > + } > +} > +EXPORT_SYMBOL(cpumask_not_dying_but);
I don't like how you create a dedicated function for a random mask. Dying mask is nothing special, right? What you really need is probably this: cpumask_andnot_any_but(mask, cpu_dying_mask, cpu);
Now, if you still think it's worth that, you can add a trivial wrapper for cpu_dying_mask. (But please pick some other name, because 'not dying but' sounds like a hangover description. :) )
Thanks, Yury
> + > /** > * cpumask_next_wrap - helper to implement for_each_cpu_wrap > * @n: the cpu prior to the place to search > -- > 2.31.1
| |