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authorNicholas Piggin <npiggin@gmail.com>2022-10-14 01:16:46 +1000
committerMichael Ellerman <mpe@ellerman.id.au>2022-10-18 22:46:18 +1100
commit2b2095f3a6b43ec36ff890febc588df1ec32e826 (patch)
tree5877fa74e049f53989a8092a507a2f8716827447 /arch/powerpc
parentb9ef323ea1682f9837bf63ba10c5e3750f71a20a (diff)
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: Nicholas Piggin <npiggin@gmail.com> Tested-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20221013151647.1857994-2-npiggin@gmail.com
Diffstat (limited to 'arch/powerpc')
-rw-r--r--arch/powerpc/mm/book3s64/hash_pgtable.c8
1 files changed, 5 insertions, 3 deletions
diff --git a/arch/powerpc/mm/book3s64/hash_pgtable.c b/arch/powerpc/mm/book3s64/hash_pgtable.c
index 747492edb75a..51f48984abca 100644
--- a/arch/powerpc/mm/book3s64/hash_pgtable.c
+++ b/arch/powerpc/mm/book3s64/hash_pgtable.c
@@ -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();