trace/pid_list: Change gfp flags in pid_list_fill_irq()

pid_list_fill_irq() runs via irq_work.
When CONFIG_PREEMPT_RT is disabled, it would run in irq_context.
so it shouldn't sleep while memory allocation.

Change gfp flags from GFP_KERNEL to GFP_NOWAIT to prevent sleep in
irq_work.

This change wouldn't impact functionality in practice because the worst-size
is 2K.

Cc: stable@goodmis.org
Fixes: 8d6e909 ("tracing: Create a sparse bitmask for pid filtering")
Link: https://lore.kernel.org/20240704150226.1359936-1-yeoreum.yun@arm.com
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: levi.yun <yeoreum.yun@arm.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Author: LeviYeoReum

kernel/trace/pid_list.c

@@ -354,7 +354,7 @@ static void pid_list_refill_irq(struct irq_work *iwork)
 	while (upper_count-- > 0) {
 		union upper_chunk *chunk;
 
-		chunk = kzalloc(sizeof(*chunk), GFP_KERNEL);
+		chunk = kzalloc(sizeof(*chunk), GFP_NOWAIT);
 		if (!chunk)
 			break;
 		*upper_next = chunk;
@@ -365,7 +365,7 @@ static void pid_list_refill_irq(struct irq_work *iwork)
 	while (lower_count-- > 0) {
 		union lower_chunk *chunk;
 
-		chunk = kzalloc(sizeof(*chunk), GFP_KERNEL);
+		chunk = kzalloc(sizeof(*chunk), GFP_NOWAIT);
 		if (!chunk)
 			break;
 		*lower_next = chunk;