The arm perf_callchain_user() functions looks at current->mm,
apparently to determine whether the thread is a kthread without any
valid user context.

In general, a non-NULL current->mm doesn't imply that current is a
kthread, as kthreads can install an mm via use_mm(), and so it's
preferable to use is_kthread() to determine whether a thread is a

For consistency, let's use is_kthread() here.

Signed-off-by: Mark Rutland <>
Cc: Will Deacon <>
Cc: Ingo Molnar <>
Cc: Peter Zijlstra <>
 arch/arm/kernel/perf_callchain.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/kernel/perf_callchain.c b/arch/arm/kernel/perf_callchain.c
index 3b69a76d341e..5c920f2c46a8 100644
--- a/arch/arm/kernel/perf_callchain.c
+++ b/arch/arm/kernel/perf_callchain.c
@@ -71,7 +71,7 @@ perf_callchain_user(struct perf_callchain_entry_ctx *entry, 
struct pt_regs *regs
        perf_callchain_store(entry, regs->ARM_pc);
-       if (!current->mm)
+       if (is_kthread(current))
        tail = (struct frame_tail __user *)regs->ARM_fp - 1;

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