From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx> When DEBUG_PREEMPT=y, exit_to_user_mode_prepare ->tick_nohz_user_enter_prepare ->tick_nohz_full_cpu(smp_processor_id()) ->smp_processor_id() ->debug_smp_processor_id() ->check preempt_count() then: [ 5.717610] BUG: using smp_processor_id() in preemptible [00000000] code: S20urandom/94 [ 5.718111] caller is debug_smp_processor_id+0x24/0x38 [ 5.718417] CPU: 1 PID: 94 Comm: S20urandom Not tainted 6.0.0-rc3-00010-gfd0a0d619c63-dirty #238 [ 5.718886] Hardware name: riscv-virtio,qemu (DT) [ 5.719136] Call Trace: [ 5.719281] [<ffffffff800055fc>] dump_backtrace+0x2c/0x3c [ 5.719566] [<ffffffff80ae6cb0>] show_stack+0x44/0x5c [ 5.720023] [<ffffffff80aee870>] dump_stack_lvl+0x74/0xa4 [ 5.720557] [<ffffffff80aee8bc>] dump_stack+0x1c/0x2c [ 5.721033] [<ffffffff80af65c0>] check_preemption_disabled+0x104/0x108 [ 5.721538] [<ffffffff80af65e8>] debug_smp_processor_id+0x24/0x38 [ 5.722001] [<ffffffff800aee30>] exit_to_user_mode_prepare+0x48/0x178 [ 5.722355] [<ffffffff80af5bf4>] irqentry_exit_to_user_mode+0x18/0x30 [ 5.722685] [<ffffffff80af5c70>] irqentry_exit+0x64/0xa4 [ 5.722953] [<ffffffff80af52f4>] do_page_fault+0x1d8/0x544 [ 5.723291] [<ffffffff80003310>] ret_from_exception+0x0/0xb8 (Above is found in riscv platform with generic_entry) The smp_processor_id() needs irqs disable or preempt_disable, so use preempt dis/in protecting the tick_nohz_user_enter_prepare(). Signed-off-by: Guo Ren <guoren@xxxxxxxxxxxxxxxxx> Signed-off-by: Guo Ren <guoren@xxxxxxxxxx> --- kernel/entry/common.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/entry/common.c b/kernel/entry/common.c index 063068a9ea9b..36e4cd50531c 100644 --- a/kernel/entry/common.c +++ b/kernel/entry/common.c @@ -194,8 +194,10 @@ static void exit_to_user_mode_prepare(struct pt_regs *regs) lockdep_assert_irqs_disabled(); + preempt_disable(); /* Flush pending rcuog wakeup before the last need_resched() check */ tick_nohz_user_enter_prepare(); + preempt_enable(); if (unlikely(ti_work & EXIT_TO_USER_MODE_WORK)) ti_work = exit_to_user_mode_loop(regs, ti_work); -- 2.36.1
