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 kthread. For consistency, let's use is_kthread() here. Signed-off-by: Mark Rutland <mark.rutl...@arm.com> Cc: Will Deacon <w...@kernel.org> Cc: Ingo Molnar <mi...@kernel.org> Cc: Peter Zijlstra <pet...@infradead.org> --- 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)) return; tail = (struct frame_tail __user *)regs->ARM_fp - 1; -- 2.11.0