On Sat, Apr 27, 2024 at 06:28:08PM +0800, Zqiang wrote: > Currently, the condition "__this_cpu_read(ksoftirqd) == current" is > checked to ensure the rcu_softirq_qs() is invoked in ksoftirqd tasks > context for non-RT kernels. however, in some scenarios, this condition > will be broken. > > ksoftirqd/0 > ->finish_task_switch > ->put_task_struct_rcu_user > ->call_rcu(&task->rcu, delayed_put_task_struct) > ->__kasan_record_aux_stack > ->pfn_valid > ->rcu_read_lock_sched() > <interrupt> > __irq_exit_rcu > ->__do_softirq > -> if (!IS_ENABLED(CONFIG_PREEMPT_RT) && > __this_cpu_read(ksoftirqd) == current) > ->rcu_softirq_qs > ->RCU_LOCKDEP_WARN(lock_is_held(&rcu_sched_lock_map)) > > The rcu quiescent states is reported occurs in the rcu-read critical > section, so the lockdep warning is triggered. this commit therefore > remove "__this_cpu_read(ksoftirqd) == current" condition check, generate > new "handle_softirqs(bool kirqd)" function to replace __do_softirq() in > run_ksoftirqdt(), and set parameter kirqd to true, make rcu_softirq_qs() > be invoked only in ksofirqd tasks context for non-RT kernels. > > Reported-by: syzbot+dce04ed6d1438ad69656@xxxxxxxxxxxxxxxxxxxxxxxxx > Link: https://lore.kernel.org/lkml/8f281a10-b85a-4586-9586-5bbc12dc784f@paulmck-laptop/T/#mea8aba4abfcb97bbf499d169ce7f30c4cff1b0e3 > Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Signed-off-by: Zqiang <qiang.zhang1211@xxxxxxxxx> Reviewed-by: Paul E. McKenney <paulmck@xxxxxxxxxx> > --- > kernel/softirq.c | 12 ++++++++---- > 1 file changed, 8 insertions(+), 4 deletions(-) > > diff --git a/kernel/softirq.c b/kernel/softirq.c > index b315b21fb28c..e991d735be0d 100644 > --- a/kernel/softirq.c > +++ b/kernel/softirq.c > @@ -508,7 +508,7 @@ static inline bool lockdep_softirq_start(void) { return false; } > static inline void lockdep_softirq_end(bool in_hardirq) { } > #endif > > -asmlinkage __visible void __softirq_entry __do_softirq(void) > +static void handle_softirqs(bool kirqd) > { > unsigned long end = jiffies + MAX_SOFTIRQ_TIME; > unsigned long old_flags = current->flags; > @@ -563,8 +563,7 @@ asmlinkage __visible void __softirq_entry __do_softirq(void) > pending >>= softirq_bit; > } > > - if (!IS_ENABLED(CONFIG_PREEMPT_RT) && > - __this_cpu_read(ksoftirqd) == current) > + if (!IS_ENABLED(CONFIG_PREEMPT_RT) && kirqd) > rcu_softirq_qs(); > > local_irq_disable(); > @@ -584,6 +583,11 @@ asmlinkage __visible void __softirq_entry __do_softirq(void) > current_restore_flags(old_flags, PF_MEMALLOC); > } > > +asmlinkage __visible void __softirq_entry __do_softirq(void) > +{ > + handle_softirqs(false); > +} > + > /** > * irq_enter_rcu - Enter an interrupt context with RCU watching > */ > @@ -921,7 +925,7 @@ static void run_ksoftirqd(unsigned int cpu) > * We can safely run softirq on inline stack, as we are not deep > * in the task stack here. > */ > - __do_softirq(); > + handle_softirqs(true); > ksoftirqd_run_end(); > cond_resched(); > return; > -- > 2.17.1 >
