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authorWander Lairson Costa <wander@redhat.com>2023-06-14 09:23:21 -0300
committerPeter Zijlstra <peterz@infradead.org>2023-07-13 15:21:48 +0200
commitd243b34459cea30cfe5f3a9b2feb44e7daff9938 (patch)
tree6f8b6921e0643bc5d762f0a5b0733f49a4b9ea4f /kernel/fork.c
parent06c2afb862f9da8dc5efa4b6076a0e48c3fbaaa5 (diff)
kernel/fork: beware of __put_task_struct() calling context
Under PREEMPT_RT, __put_task_struct() indirectly acquires sleeping locks. Therefore, it can't be called from an non-preemptible context. One practical example is splat inside inactive_task_timer(), which is called in a interrupt context: CPU: 1 PID: 2848 Comm: life Kdump: loaded Tainted: G W --------- Hardware name: HP ProLiant DL388p Gen8, BIOS P70 07/15/2012 Call Trace: dump_stack_lvl+0x57/0x7d mark_lock_irq.cold+0x33/0xba mark_lock+0x1e7/0x400 mark_usage+0x11d/0x140 __lock_acquire+0x30d/0x930 lock_acquire.part.0+0x9c/0x210 rt_spin_lock+0x27/0xe0 refill_obj_stock+0x3d/0x3a0 kmem_cache_free+0x357/0x560 inactive_task_timer+0x1ad/0x340 __run_hrtimer+0x8a/0x1a0 __hrtimer_run_queues+0x91/0x130 hrtimer_interrupt+0x10f/0x220 __sysvec_apic_timer_interrupt+0x7b/0xd0 sysvec_apic_timer_interrupt+0x4f/0xd0 asm_sysvec_apic_timer_interrupt+0x12/0x20 RIP: 0033:0x7fff196bf6f5 Instead of calling __put_task_struct() directly, we defer it using call_rcu(). A more natural approach would use a workqueue, but since in PREEMPT_RT, we can't allocate dynamic memory from atomic context, the code would become more complex because we would need to put the work_struct instance in the task_struct and initialize it when we allocate a new task_struct. The issue is reproducible with stress-ng: while true; do stress-ng --sched deadline --sched-period 1000000000 \ --sched-runtime 800000000 --sched-deadline \ 1000000000 --mmapfork 23 -t 20 done Reported-by: Hu Chunyu <chuhu@redhat.com> Suggested-by: Oleg Nesterov <oleg@redhat.com> Suggested-by: Valentin Schneider <vschneid@redhat.com> Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Wander Lairson Costa <wander@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20230614122323.37957-2-wander@redhat.com
Diffstat (limited to 'kernel/fork.c')
-rw-r--r--kernel/fork.c8
1 files changed, 8 insertions, 0 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index d2e12b6d2b18..f81149739eb9 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -985,6 +985,14 @@ void __put_task_struct(struct task_struct *tsk)
}
EXPORT_SYMBOL_GPL(__put_task_struct);
+void __put_task_struct_rcu_cb(struct rcu_head *rhp)
+{
+ struct task_struct *task = container_of(rhp, struct task_struct, rcu);
+
+ __put_task_struct(task);
+}
+EXPORT_SYMBOL_GPL(__put_task_struct_rcu_cb);
+
void __init __weak arch_task_cache_init(void) { }
/*