[PATCH 2/7] printk: Use consoles_suspended flag when suspending/resuming all consoles

Marcos Paulo de Souza
2025-06-07T02:54:11Z

Instead of update a per-console CON_SUSPENDED flag, use the console_list
locks to protect this flag. This is also applied to console_is_usable
functions, which now also checks if consoles_suspend is set.

Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
---
kernel/printk/internal.h | 7 ++++++-
kernel/printk/nbcon.c | 8 ++++----
kernel/printk/printk.c | 23 ++++++++++-------------
3 files changed, 20 insertions(+), 18 deletions(-)

diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h
index 48a24e7b309db20fdd7419f7aeda68ea7c79fd80..752101904f44b13059b6a922519d88e24c9f32c0 100644
--- a/kernel/printk/internal.h
+++ b/kernel/printk/internal.h
@@ -118,8 +118,12 @@ void nbcon_kthreads_wake(void);
* which can also play a role in deciding if @con can be used to print
* records.
*/
-static inline bool console_is_usable(struct console *con, short flags, bool use_atomic)
+static inline bool console_is_usable(struct console *con, short flags,
+ bool use_atomic, bool consoles_suspended)
{
+ if (consoles_suspended)
+ return false;
+
if (!(flags & CON_ENABLED))
return false;

@@ -212,6 +216,7 @@ extern bool have_boot_console;
extern bool have_nbcon_console;
extern bool have_legacy_console;
extern bool legacy_allow_panic_sync;
+extern bool consoles_suspended;

/**
* struct console_flush_type - Define available console flush methods
diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c
index fd12efcc4aeda8883773d9807bc215f6e5cdf71a..72de12396e6f1bc5234acfdf6dcc393acf88d216 100644
--- a/kernel/printk/nbcon.c
+++ b/kernel/printk/nbcon.c
@@ -1147,7 +1147,7 @@ static bool nbcon_kthread_should_wakeup(struct console *con, struct nbcon_contex
cookie = console_srcu_read_lock();

flags = console_srcu_read_flags(con);
- if (console_is_usable(con, flags, false)) {
+ if (console_is_usable(con, flags, false, consoles_suspended)) {
/* Bring the sequence in @ctxt up to date */
ctxt->seq = nbcon_seq_read(con);

@@ -1206,7 +1206,7 @@ static int nbcon_kthread_func(void *__console)

con_flags = console_srcu_read_flags(con);

- if (console_is_usable(con, con_flags, false))
+ if (console_is_usable(con, con_flags, false, consoles_suspended))
backlog = nbcon_emit_one(&wctxt, false);

console_srcu_read_unlock(cookie);
@@ -1584,7 +1584,7 @@ static void __nbcon_atomic_flush_pending(u64 stop_seq, bool allow_unsafe_takeove
if (!(flags & CON_NBCON))
continue;

- if (!console_is_usable(con, flags, true))
+ if (!console_is_usable(con, flags, true, consoles_suspended))
continue;

if (nbcon_seq_read(con) >= stop_seq)
@@ -1795,7 +1795,7 @@ void nbcon_device_release(struct console *con)
*/
cookie = console_srcu_read_lock();
printk_get_console_flush_type(&ft);
- if (console_is_usable(con, console_srcu_read_flags(con), true) &&
+ if (console_is_usable(con, console_srcu_read_flags(con), true, consoles_suspended) &&
!ft.nbcon_offload &&
prb_read_valid(prb, nbcon_seq_read(con), NULL)) {
/*
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 6d3cf488f4261a3dfd8809a5ab7164b218238c13..658acf92aa3d2a3d1e294b7e17e5ee96d8169afe 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -241,7 +241,7 @@ int devkmsg_sysctl_set_loglvl(const struct ctl_table *table, int write,
/**
* console_list_lock - Lock the console list
*
- * For console list or console->flags updates
+ * For console list, console->flags and consoles_suspended updates
*/
void console_list_lock(void)
{
@@ -383,6 +383,8 @@ bool other_cpu_in_panic(void)
*/
static int console_locked;

+bool consoles_suspended;
+
/*
* Array of consoles built from command line options (console=)
*/
@@ -2755,16 +2757,13 @@ MODULE_PARM_DESC(console_no_auto_verbose, "Disable console loglevel raise to hig
*/
void console_suspend_all(void)
{
- struct console *con;
-
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)
- console_srcu_write_flags(con, con->flags | CON_SUSPENDED);
+ consoles_suspended = true;
console_list_unlock();

/*
@@ -2779,14 +2778,12 @@ void console_suspend_all(void)
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);
+ consoles_suspended = false;
console_list_unlock();

/*
@@ -3214,7 +3211,7 @@ static bool console_flush_all(bool do_cond_resched, u64 *next_seq, bool *handove
if ((flags & CON_NBCON) && (ft.nbcon_atomic || ft.nbcon_offload))
continue;

- if (!console_is_usable(con, flags, !do_cond_resched))
+ if (!console_is_usable(con, flags, !do_cond_resched, consoles_suspended))
continue;
any_usable = true;

@@ -3604,7 +3601,7 @@ static bool legacy_kthread_should_wakeup(void)
if ((flags & CON_NBCON) && (ft.nbcon_atomic || ft.nbcon_offload))
continue;

- if (!console_is_usable(con, flags, false))
+ if (!console_is_usable(con, flags, false, consoles_suspended))
continue;

if (flags & CON_NBCON) {
@@ -4165,7 +4162,7 @@ static int unregister_console_locked(struct console *console)

if (!console_is_registered_locked(console))
res = -ENODEV;
- else if (console_is_usable(console, console->flags, true))
+ else if (console_is_usable(console, console->flags, true, consoles_suspended))
__pr_flush(console, 1000, true);

/* Disable it unconditionally */
@@ -4445,8 +4442,8 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre
* that they make forward progress, so only increment
* @diff for usable consoles.
*/
- if (!console_is_usable(c, flags, true) &&
- !console_is_usable(c, flags, false)) {
+ if (!console_is_usable(c, flags, true, consoles_suspended) &&
+ !console_is_usable(c, flags, false, consoles_suspended)) {
continue;
}

--
2.49.0