admin/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2025-12-07 20:06:24 +00:00
Code Issues Packages Projects Releases Wiki Activity

printk: Avoid scheduling irq_work on suspend

Browse Source 
Allowing irq_work to be scheduled while trying to suspend has shown
to cause problems as some architectures interpret the pending
interrupts as a reason to not suspend. This became a problem for
printk() with the introduction of NBCON consoles. With every
printk() call, NBCON console printing kthreads are woken by queueing
irq_work. This means that irq_work continues to be queued due to
printk() calls late in the suspend procedure.

Avoid this problem by preventing printk() from queueing irq_work
once console suspending has begun. This applies to triggering NBCON
and legacy deferred printing as well as klogd waiters.

Since triggering of NBCON threaded printing relies on irq_work, the
pr_flush() within console_suspend_all() is used to perform the final
flushing before suspending consoles and blocking irq_work queueing.
NBCON consoles that are not suspended (due to the usage of the
"no_console_suspend" boot argument) transition to atomic flushing.

Introduce a new global variable @console_irqwork_blocked to flag
when irq_work queueing is to be avoided. The flag is used by
printk_get_console_flush_type() to avoid allowing deferred printing
and switch NBCON consoles to atomic flushing. It is also used by
vprintk_emit() to avoid klogd waking.

Add WARN_ON_ONCE(console_irqwork_blocked) to the irq_work queuing
functions to catch any code that attempts to queue printk irq_work
during the suspending/resuming procedure.

Cc: stable@vger.kernel.org # 6.13.x because no drivers in 6.12.x
Fixes: 6b93bb41f6 ("printk: Add non-BKL (nbcon) console basic infrastructure")
Closes: https://lore.kernel.org/lkml/DB9PR04MB8429E7DDF2D93C2695DE401D92C4A@DB9PR04MB8429.eurprd04.prod.outlook.com
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Tested-by: Sherry Sun <sherry.sun@nxp.com>
Link: https://patch.msgid.link/20251113160351.113031-3-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
This commit is contained in:
John Ogness
2025-11-13 17:09:48 +01:06
committed by Petr Mladek
parent d01ff281bd
commit 26873e3e7f
3 changed files with 55 additions and 18 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
kernel/printk/internal.h
View File

@@ -230,6 +230,8 @@ struct console_flush_type {
bool legacy_offload;
};
extern bool console_irqwork_blocked;
/*
* Identify which console flushing methods should be used in the context of
* the caller.
@@ -241,7 +243,7 @@ static inline void printk_get_console_flush_type(struct console_flush_type *ft)
switch (nbcon_get_default_prio()) {
case NBCON_PRIO_NORMAL:
if (have_nbcon_console && !have_boot_console) {
if (printk_kthreads_running)
if (printk_kthreads_running && !console_irqwork_blocked)
ft->nbcon_offload = true;
else
ft->nbcon_atomic = true;
@@ -251,7 +253,7 @@ static inline void printk_get_console_flush_type(struct console_flush_type *ft)
if (have_legacy_console || have_boot_console) {
if (!is_printk_legacy_deferred())
ft->legacy_direct = true;
else
else if (!console_irqwork_blocked)
ft->legacy_offload = true;
}
break;
@@ -264,7 +266,7 @@ static inline void printk_get_console_flush_type(struct console_flush_type *ft)
if (have_legacy_console || have_boot_console) {
if (!is_printk_legacy_deferred())
ft->legacy_direct = true;
else
else if (!console_irqwork_blocked)
ft->legacy_offload = true;
}
break;

7
kernel/printk/nbcon.c
View File

@@ -1276,6 +1276,13 @@ void nbcon_kthreads_wake(void)
if (!printk_kthreads_running)
return;
/*
* It is not allowed to call this function when console irq_work
* is blocked.
*/
if (WARN_ON_ONCE(console_irqwork_blocked))
return;
cookie = console_srcu_read_lock();
for_each_console_srcu(con) {
if (!(console_srcu_read_flags(con) & CON_NBCON))

58
kernel/printk/printk.c
View File

@@ -462,6 +462,9 @@ bool have_boot_console;
/* See printk_legacy_allow_panic_sync() for details. */
bool legacy_allow_panic_sync;
/* Avoid using irq_work when suspending. */
bool console_irqwork_blocked;
#ifdef CONFIG_PRINTK
DECLARE_WAIT_QUEUE_HEAD(log_wait);
static DECLARE_WAIT_QUEUE_HEAD(legacy_wait);
@@ -2426,7 +2429,7 @@ asmlinkage int vprintk_emit(int facility, int level,
if (ft.legacy_offload)
defer_console_output();
else
else if (!console_irqwork_blocked)
wake_up_klogd();
return printed_len;
@@ -2730,10 +2733,20 @@ void console_suspend_all(void)
{
struct console *con;
if (console_suspend_enabled)
pr_info("Suspending console(s) (use no_console_suspend to debug)\n");
/*
* Flush any console backlog and then avoid queueing irq_work until
* console_resume_all(). Until then deferred printing is no longer
* triggered, NBCON consoles transition to atomic flushing, and
* any klogd waiters are not triggered.
*/
pr_flush(1000, true);
console_irqwork_blocked = true;
if (!console_suspend_enabled)
return;
pr_info("Suspending console(s) (use no_console_suspend to debug)\n");
pr_flush(1000, true);
console_list_lock();
for_each_console(con)
@@ -2754,26 +2767,34 @@ void console_resume_all(void)
struct console_flush_type ft;
struct console *con;
if (!console_suspend_enabled)
return;
console_list_lock();
for_each_console(con)
console_srcu_write_flags(con, con->flags & ~CON_SUSPENDED);
console_list_unlock();
/*
* Ensure that all SRCU list walks have completed. All printing
* contexts must be able to see they are no longer suspended so
* that they are guaranteed to wake up and resume printing.
* Allow queueing irq_work. After restoring console state, deferred
* printing and any klogd waiters need to be triggered in case there
* is now a console backlog.
*/
synchronize_srcu(&console_srcu);
console_irqwork_blocked = false;
if (console_suspend_enabled) {
console_list_lock();
for_each_console(con)
console_srcu_write_flags(con, con->flags & ~CON_SUSPENDED);
console_list_unlock();
/*
* Ensure that all SRCU list walks have completed. All printing
* contexts must be able to see they are no longer suspended so
* that they are guaranteed to wake up and resume printing.
*/
synchronize_srcu(&console_srcu);
}
printk_get_console_flush_type(&ft);
if (ft.nbcon_offload)
nbcon_kthreads_wake();
if (ft.legacy_offload)
defer_console_output();
else
wake_up_klogd();
pr_flush(1000, true);
}
@@ -4511,6 +4532,13 @@ static void __wake_up_klogd(int val)
if (!printk_percpu_data_ready())
return;
/*
* It is not allowed to call this function when console irq_work
* is blocked.
*/
if (WARN_ON_ONCE(console_irqwork_blocked))
return;
preempt_disable();
/*
* Guarantee any new records can be seen by tasks preparing to wait