On 19/07/22 22:11, Jason A. Donenfeld wrote:
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index c46f3a63b758..f164098fb614 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1936,6 +1936,7 @@ extern struct task_struct *find_get_task_by_vpid(pid_t nr);
>
> extern int wake_up_state(struct task_struct *tsk, unsigned int state);
> extern int wake_up_process(struct task_struct *tsk);
> +extern int wake_up_task_interruptible(struct task_struct *tsk);
> extern void wake_up_new_task(struct task_struct *tsk);
>
> #ifdef CONFIG_SMP
> diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h
> index cafbe03eed01..56a15f35e7b3 100644
> --- a/include/linux/sched/signal.h
> +++ b/include/linux/sched/signal.h
> @@ -364,7 +364,7 @@ static inline void clear_notify_signal(void)
> static inline bool __set_notify_signal(struct task_struct *task)
> {
> return !test_and_set_tsk_thread_flag(task, TIF_NOTIFY_SIGNAL) &&
> - !wake_up_state(task, TASK_INTERRUPTIBLE);
> + !wake_up_task_interruptible(task);
> }
>
> /*
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index da0bf6fe9ecd..b178940185d7 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -4280,6 +4280,12 @@ int wake_up_process(struct task_struct *p)
> }
> EXPORT_SYMBOL(wake_up_process);
>
> +int wake_up_task_interruptible(struct task_struct *p)
> +{
> + return try_to_wake_up(p, TASK_INTERRUPTIBLE, 0);
> +}
> +EXPORT_SYMBOL_GPL(wake_up_task_interruptible);
> +
> int wake_up_state(struct task_struct *p, unsigned int state)
> {
> return try_to_wake_up(p, state, 0);
> --
> 2.35.1
The sched changes are unfortunate, as I had understood it the alternative
would be fixing all sleeping hwrng's to make them have a proper wait
pattern that doesn't require being sent a signal to avoid missing events,
i.e. instead of
hwrng->read(): devm_hwrng_unregister():
schedule_timeout_interruptible(x); set_notify_signal(waiting_reader);
do
hwrng->read(): devm_hwrng_unregister():
set_current_state(TASK_INTERRUPTIBLE) rng->dying = true;
if (!rng->dying) wake_up_process(waiting_reader);
schedule_timeout(x);
I had initially convinced myself this would be somewhat involved, but
writing the above I thought maybe not... The below is applied on top of
your v10, would you be able to test whether it actually works?
I apologize for telling you to do one thing and then suggesting something else...
IMO set_notify_signal() is for interrupting tasks that are in a wait-loop
that has nothing to do with the calling code (e.g. task_work, I assume
livepatching does that for the same reason), but here it's hwrng core code
interrupting a sleeping hwrng device.
It does however mean patching up any sleeping hwrng (a quick search tells
me there are more, e.g. npcm-rng does readb_poll_timeout())
---
diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index df45c265878e..40a73490bfdc 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -522,9 +522,12 @@ static int hwrng_fillfn(void *unused)
break;
if (rc <= 0) {
- if (kthread_should_stop())
+ set_current_state(TASK_INTERRUPTIBLE);
+ if (kthread_should_stop()) {
+ __set_current_state(TASK_RUNNING);
break;
- schedule_timeout_interruptible(HZ * 10);
+ }
+ schedule_timeout(HZ * 10);
continue;
}
@@ -581,6 +584,8 @@ int hwrng_register(struct hwrng *rng)
init_completion(&rng->cleanup_done);
complete(&rng->cleanup_done);
+ rng->unregistering = false;
+
if (!current_rng ||
(!cur_rng_set_by_user && rng->quality > current_rng->quality)) {
/*
@@ -630,8 +635,10 @@ void hwrng_unregister(struct hwrng *rng)
rcu_read_lock();
waiting_reader = xchg(¤t_waiting_reader, UNREGISTERING_READER);
- if (waiting_reader && waiting_reader != UNREGISTERING_READER)
- set_notify_signal(waiting_reader);
+ if (waiting_reader && waiting_reader != UNREGISTERING_READER) {
+ rng->unregistering = true;
+ wake_up_process(waiting_reader);
+ }
rcu_read_unlock();
old_rng = current_rng;
list_del(&rng->list);
diff --git a/drivers/net/wireless/ath/ath9k/rng.c b/drivers/net/wireless/ath/ath9k/rng.c
index 8980dc36509e..35cac38054b5 100644
--- a/drivers/net/wireless/ath/ath9k/rng.c
+++ b/drivers/net/wireless/ath/ath9k/rng.c
@@ -75,9 +75,17 @@ static int ath9k_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
bytes_read += max & 3UL;
memzero_explicit(&word, sizeof(word));
}
- if (!wait || !max || likely(bytes_read) || fail_stats > 110 ||
- ((current->flags & PF_KTHREAD) && kthread_should_stop()) ||
- schedule_timeout_interruptible(ath9k_rng_delay_get(++fail_stats)))
+ if (!wait || !max || likely(bytes_read) || fail_stats > 110)
+ break;
+
+ set_current_state(TASK_INTERRUPTIBLE);
+ if (rng->unregistering ||
+ ((current->flags & PF_KTHREAD) && kthread_should_stop())) {
+ __set_current_state(TASK_RUNNING);
+ break;
+ }
+
+ if (schedule_timeout(ath9k_rng_delay_get(++fail_stats)))
break;
}
diff --git a/include/linux/hw_random.h b/include/linux/hw_random.h
index aa1d4da03538..778f10dfa12b 100644
--- a/include/linux/hw_random.h
+++ b/include/linux/hw_random.h
@@ -45,6 +45,7 @@ struct hwrng {
int (*read)(struct hwrng *rng, void *data, size_t max, bool wait);
unsigned long priv;
unsigned short quality;
+ int unregistering;
/* internal. */
struct list_head list;
diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h
index 56a15f35e7b3..9b94a8f18b04 100644
--- a/include/linux/sched/signal.h
+++ b/include/linux/sched/signal.h
@@ -364,7 +364,7 @@ static inline void clear_notify_signal(void)
static inline bool __set_notify_signal(struct task_struct *task)
{
return !test_and_set_tsk_thread_flag(task, TIF_NOTIFY_SIGNAL) &&
- !wake_up_task_interruptible(task);
+ !wake_up_state(task, TASK_INTERRUPTIBLE);
}
/*
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e3e675eef63d..a463dbc92fcd 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4279,12 +4279,6 @@ int wake_up_process(struct task_struct *p)
}
EXPORT_SYMBOL(wake_up_process);
-int wake_up_task_interruptible(struct task_struct *p)
-{
- return try_to_wake_up(p, TASK_INTERRUPTIBLE, 0);
-}
-EXPORT_SYMBOL_GPL(wake_up_task_interruptible);
-
int wake_up_state(struct task_struct *p, unsigned int state)
{
return try_to_wake_up(p, state, 0);
