[PATCH v13 03/11] perf: Use current->flags & PF_KTHREAD|PF_USER_WORKER instead of current->mm == NULL

[Steven Rostedt <rostedt@kernel.org>]

From: Steven Rostedt <rostedt@goodmis.org>

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.

Link: https://lore.kernel.org/linux-trace-kernel/20250424163607.GE18306@noisy.programming.kicks-ass.net/
Link: https://lore.kernel.org/all/20250624130744.602c5b5f@batman.local.home/

Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
Changes since v11: https://lore.kernel.org/20250625231622.172100822@goodmis.org

- Also check against PF_USER_WORKER as io workers do not have PF_KTHREAD
  set.

 kernel/events/callchain.c | 6 +++---
 kernel/events/core.c      | 4 ++--
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c
index cd0e3fc7ed05..5982d18f169b 100644
--- a/kernel/events/callchain.c
+++ b/kernel/events/callchain.c
@@ -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) {
diff --git a/kernel/events/core.c b/kernel/events/core.c
index b2a53cabcb17..cf35dc707ad5 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7414,7 +7414,7 @@ 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;
@@ -8054,7 +8054,7 @@ 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)) {
 			struct page *p;
 
 			pagefault_disable();
-- 
2.47.2