On Thu, May 05, 2022 at 11:32:04AM -0700, Luck, Tony wrote: > Patch now looks like this. Author credit to Peter ... are you willing > to add a Signed-off-by to stop checkpatch from whining at me? sure, see below. > There isn't a "Something-similar-suggested-by:" tag to credit Thomas > with this. Perhaps "Inspired-by:"? I'm all for creative one off tags, there's some marvelous ones in the tree, but we always need more :-) > -Tony > > > From df5ca8024997d3d782978d154cfbff5147f451ad Mon Sep 17 00:00:00 2001 > From: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > Date: Thu, 5 May 2022 08:55:09 -0700 > Subject: [PATCH] stop_machine: Add stop_core_cpuslocked() for per-core > operations > > Hardware core level testing features require near simultaneous execution > of WRMSR instructions on all threads of a core to initiate a test. > > Provide a customized cut down version of stop_machine_cpuslocked() that > just operates on the threads of a single core. > Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> > Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx> > --- > include/linux/stop_machine.h | 16 ++++++++++++++++ > kernel/stop_machine.c | 19 +++++++++++++++++++ > 2 files changed, 35 insertions(+) > > diff --git a/include/linux/stop_machine.h b/include/linux/stop_machine.h > index 46fb3ebdd16e..ea7a74ea7389 100644 > --- a/include/linux/stop_machine.h > +++ b/include/linux/stop_machine.h > @@ -124,6 +124,22 @@ int stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus); > */ > int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus); > > +/** > + * stop_core_cpuslocked: - stop all threads on just one core > + * @cpu: any cpu in the targeted core > + * @fn: the function to run > + * @data: the data ptr for @fn() > + * > + * Same as above, but instead of every CPU, only the logical CPUs of a > + * single core are affected. > + * > + * Context: Must be called from within a cpus_read_lock() protected region. > + * > + * Return: 0 if all executions of @fn returned 0, any non zero return > + * value if any returned non zero. > + */ > +int stop_core_cpuslocked(unsigned int cpu, cpu_stop_fn_t fn, void *data); > + > int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data, > const struct cpumask *cpus); > #else /* CONFIG_SMP || CONFIG_HOTPLUG_CPU */ > diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c > index cbc30271ea4d..579761729836 100644 > --- a/kernel/stop_machine.c > +++ b/kernel/stop_machine.c > @@ -633,6 +633,25 @@ int stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus) > } > EXPORT_SYMBOL_GPL(stop_machine); > > +int stop_core_cpuslocked(unsigned int cpu, cpu_stop_fn_t fn, void *data) > +{ > + const struct cpumask *smt_mask = cpu_smt_mask(cpu); > + > + struct multi_stop_data msdata = { > + .fn = fn, > + .data = data, > + .num_threads = cpumask_weight(smt_mask), > + .active_cpus = smt_mask, > + }; > + > + lockdep_assert_cpus_held(); > + > + /* Set the initial state and stop all online cpus. */ > + set_state(&msdata, MULTI_STOP_PREPARE); > + return stop_cpus(smt_mask, multi_cpu_stop, &msdata); > +} > +EXPORT_SYMBOL_GPL(stop_core_cpuslocked); > + > /** > * stop_machine_from_inactive_cpu - stop_machine() from inactive CPU > * @fn: the function to run > -- > 2.35.1 >