diff options
| author | Nicholas Piggin <npiggin@gmail.com> | 2022-10-13 17:16:46 +0200 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2022-10-18 13:46:18 +0200 |
| commit | 2b2095f3a6b43ec36ff890febc588df1ec32e826 (patch) | |
| tree | 5877fa74e049f53989a8092a507a2f8716827447 | |
| parent | powerpc/64s: Disable preemption in hash lazy mmu mode (diff) | |
| download | linux-2b2095f3a6b43ec36ff890febc588df1ec32e826.tar.xz linux-2b2095f3a6b43ec36ff890febc588df1ec32e826.zip | |
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
| -rw-r--r-- | arch/powerpc/mm/book3s64/hash_pgtable.c | 8 |
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(); |