Commit 2b2095f3 authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Michael Ellerman
Browse files

powerpc/64s: Fix hash__change_memory_range preemption warning 



stop_machine_cpuslocked takes a mutex so it must be called in a
preemptible context, so it can't simply be fixed by disabling
preemption.

This is not a bug, because CPU hotplug is locked, so this processor will
call in to the stop machine function. So raw_smp_processor_id() could be
used. This leaves a small chance that this thread will be migrated to
another CPU, so the master work would be done by a CPU from a different
context. Better for test coverage to make that a common case by just
having the first CPU to call in become the master.

Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
Tested-by: default avatarGuenter Roeck <linux@roeck-us.net>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20221013151647.1857994-2-npiggin@gmail.com
parent b9ef323e

arch/powerpc/mm/book3s64/hash_pgtable.c

+5 −3
Original line number Diff line number Diff line
@@ -404,7 +404,8 @@ EXPORT_SYMBOL_GPL(hash__has_transparent_hugepage); 


struct change_memory_parms {

	unsigned long start, end, newpp;

	unsigned int step, nr_cpus, master_cpu;

	unsigned int step, nr_cpus;

	atomic_t master_cpu;

	atomic_t cpu_counter;

};
@@ -478,7 +479,8 @@ static int change_memory_range_fn(void *data) 
{

	struct change_memory_parms *parms = data;



	if (parms->master_cpu != smp_processor_id())

	// First CPU goes through, all others wait.

	if (atomic_xchg(&parms->master_cpu, 1) == 1)

		return chmem_secondary_loop(parms);



	// Wait for all but one CPU (this one) to call-in
@@ -516,7 +518,7 @@ static bool hash__change_memory_range(unsigned long start, unsigned long end, 
		chmem_parms.end = end;

		chmem_parms.step = step;

		chmem_parms.newpp = newpp;

		chmem_parms.master_cpu = smp_processor_id();

		atomic_set(&chmem_parms.master_cpu, 0);



		cpus_read_lock();