Commit 90942f9f authored Aug 20, 2025 by Steven Rostedt Committed by Peter Zijlstra Aug 26, 2025

perf: Use current->flags & PF_KTHREAD|PF_USER_WORKER instead of current->mm == NULL



To determine if a task is a kernel thread or not, it is more reliable to
use (current->flags & (PF_KTHREAD|PF_USER_WORKERi)) than to rely on
current->mm being NULL.  That is because some kernel tasks (io_uring
helpers) may have a mm field.

Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250820180428.592367294@kernel.org

parent 153f9e74

kernel/events/callchain.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -246,10 +246,10 @@ get_perf_callchain(struct pt_regs *regs, bool kernel, bool user,

		if (user && !crosstask) {
		if (!user_mode(regs)) {
		if (current->mm)
		regs = task_pt_regs(current);
		else
		if (current->flags & (PF_KTHREAD \| PF_USER_WORKER))
		regs = NULL;
		else
		regs = task_pt_regs(current);
		}

		if (regs) {

kernel/events/core.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -7446,7 +7446,7 @@ static void perf_sample_regs_user(struct perf_regs *regs_user,
		if (user_mode(regs)) {
		regs_user->abi = perf_reg_abi(current);
		regs_user->regs = regs;
		} else if (!(current->flags & PF_KTHREAD)) {
		} else if (!(current->flags & (PF_KTHREAD \| PF_USER_WORKER))) {
		perf_get_regs_user(regs_user, regs);
		} else {
		regs_user->abi = PERF_SAMPLE_REGS_ABI_NONE;
		@@ -8086,7 +8086,7 @@ static u64 perf_virt_to_phys(u64 virt)
		* Try IRQ-safe get_user_page_fast_only first.
		* If failed, leave phys_addr as 0.
		*/
		if (current->mm != NULL) {
		if (!(current->flags & (PF_KTHREAD \| PF_USER_WORKER))) {
		struct page *p;

		pagefault_disable();