[PATCH AUTOSEL 6.1 1/3] printk: Keep non-panic-CPUs out of console lock

[PATCH AUTOSEL 6.1 1/3] printk: Keep non-panic-CPUs out of console lock

[Sasha Levin]

From: John Ogness <john.ogness@linutronix.de>

[ Upstream commit 51a1d258e50e03a0216bf42b6af9ff34ec402ac1 ]

When in a panic situation, non-panic CPUs should avoid holding the
console lock so as not to contend with the panic CPU. This is already
implemented with abandon_console_lock_in_panic(), which is checked
after each printed line. However, non-panic CPUs should also avoid
trying to acquire the console lock during a panic.

Modify console_trylock() to fail and console_lock() to block() when
called from a non-panic CPU during a panic.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20230717194607.145135-4-john.ogness@linutronix.de
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 kernel/printk/printk.c | 45 ++++++++++++++++++++++++------------------
 1 file changed, 26 insertions(+), 19 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index e4f1e7478b521..4b9429f3fd6d8 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2552,6 +2552,25 @@ static int console_cpu_notify(unsigned int cpu)
 	return 0;
 }
 
+/*
+ * Return true when this CPU should unlock console_sem without pushing all
+ * messages to the console. This reduces the chance that the console is
+ * locked when the panic CPU tries to use it.
+ */
+static bool abandon_console_lock_in_panic(void)
+{
+	if (!panic_in_progress())
+		return false;
+
+	/*
+	 * We can use raw_smp_processor_id() here because it is impossible for
+	 * the task to be migrated to the panic_cpu, or away from it. If
+	 * panic_cpu has already been set, and we're not currently executing on
+	 * that CPU, then we never will be.
+	 */
+	return atomic_read(&panic_cpu) != raw_smp_processor_id();
+}
+
 /**
  * console_lock - lock the console system for exclusive use.
  *
@@ -2564,6 +2583,10 @@ void console_lock(void)
 {
 	might_sleep();
 
+	/* On panic, the console_lock must be left to the panic cpu. */
+	while (abandon_console_lock_in_panic())
+		msleep(1000);
+
 	down_console_sem();
 	if (console_suspended)
 		return;
@@ -2582,6 +2605,9 @@ EXPORT_SYMBOL(console_lock);
  */
 int console_trylock(void)
 {
+	/* On panic, the console_lock must be left to the panic cpu. */
+	if (abandon_console_lock_in_panic())
+		return 0;
 	if (down_trylock_console_sem())
 		return 0;
 	if (console_suspended) {
@@ -2600,25 +2626,6 @@ int is_console_locked(void)
 }
 EXPORT_SYMBOL(is_console_locked);
 
-/*
- * Return true when this CPU should unlock console_sem without pushing all
- * messages to the console. This reduces the chance that the console is
- * locked when the panic CPU tries to use it.
- */
-static bool abandon_console_lock_in_panic(void)
-{
-	if (!panic_in_progress())
-		return false;
-
-	/*
-	 * We can use raw_smp_processor_id() here because it is impossible for
-	 * the task to be migrated to the panic_cpu, or away from it. If
-	 * panic_cpu has already been set, and we're not currently executing on
-	 * that CPU, then we never will be.
-	 */
-	return atomic_read(&panic_cpu) != raw_smp_processor_id();
-}
-
 /*
  * Check if the given console is currently capable and allowed to print
  * records.
-- 
2.40.1

[PATCH AUTOSEL 6.1 2/3] printk: Consolidate console deferred printing

[Sasha Levin]

From: John Ogness <john.ogness@linutronix.de>

[ Upstream commit 696ffaf50e1f8dbc66223ff614473f945f5fb8d8 ]

Printing to consoles can be deferred for several reasons:

- explicitly with printk_deferred()
- printk() in NMI context
- recursive printk() calls

The current implementation is not consistent. For printk_deferred(),
irq work is scheduled twice. For NMI und recursive, panic CPU
suppression and caller delays are not properly enforced.

Correct these inconsistencies by consolidating the deferred printing
code so that vprintk_deferred() is the top-level function for
deferred printing and vprintk_emit() will perform whichever irq_work
queueing is appropriate.

Also add kerneldoc for wake_up_klogd() and defer_console_output() to
clarify their differences and appropriate usage.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20230717194607.145135-6-john.ogness@linutronix.de
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 kernel/printk/printk.c      | 35 ++++++++++++++++++++++++++++-------
 kernel/printk/printk_safe.c |  9 ++-------
 2 files changed, 30 insertions(+), 14 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 4b9429f3fd6d8..cc53fb77f77cc 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2269,7 +2269,11 @@ asmlinkage int vprintk_emit(int facility, int level,
 		preempt_enable();
 	}
 
-	wake_up_klogd();
+	if (in_sched)
+		defer_console_output();
+	else
+		wake_up_klogd();
+
 	return printed_len;
 }
 EXPORT_SYMBOL(vprintk_emit);
@@ -3490,11 +3494,33 @@ static void __wake_up_klogd(int val)
 	preempt_enable();
 }
 
+/**
+ * wake_up_klogd - Wake kernel logging daemon
+ *
+ * Use this function when new records have been added to the ringbuffer
+ * and the console printing of those records has already occurred or is
+ * known to be handled by some other context. This function will only
+ * wake the logging daemon.
+ *
+ * Context: Any context.
+ */
 void wake_up_klogd(void)
 {
 	__wake_up_klogd(PRINTK_PENDING_WAKEUP);
 }
 
+/**
+ * defer_console_output - Wake kernel logging daemon and trigger
+ *	console printing in a deferred context
+ *
+ * Use this function when new records have been added to the ringbuffer,
+ * this context is responsible for console printing those records, but
+ * the current context is not allowed to perform the console printing.
+ * Trigger an irq_work context to perform the console printing. This
+ * function also wakes the logging daemon.
+ *
+ * Context: Any context.
+ */
 void defer_console_output(void)
 {
 	/*
@@ -3511,12 +3537,7 @@ void printk_trigger_flush(void)
 
 int vprintk_deferred(const char *fmt, va_list args)
 {
-	int r;
-
-	r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, fmt, args);
-	defer_console_output();
-
-	return r;
+	return vprintk_emit(0, LOGLEVEL_SCHED, NULL, fmt, args);
 }
 
 int _printk_deferred(const char *fmt, ...)
diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c
index ef0f9a2044da1..6d10927a07d83 100644
--- a/kernel/printk/printk_safe.c
+++ b/kernel/printk/printk_safe.c
@@ -38,13 +38,8 @@ asmlinkage int vprintk(const char *fmt, va_list args)
 	 * Use the main logbuf even in NMI. But avoid calling console
 	 * drivers that might have their own locks.
 	 */
-	if (this_cpu_read(printk_context) || in_nmi()) {
-		int len;
-
-		len = vprintk_store(0, LOGLEVEL_DEFAULT, NULL, fmt, args);
-		defer_console_output();
-		return len;
-	}
+	if (this_cpu_read(printk_context) || in_nmi())
+		return vprintk_deferred(fmt, args);
 
 	/* No obstacles. */
 	return vprintk_default(fmt, args);
-- 
2.40.1

[PATCH AUTOSEL 6.1 3/3] thermal/drivers/sun8i: Free calibration nvmem after reading it

[Sasha Levin]

From: Mark Brown <broonie@kernel.org>

[ Upstream commit c51592a95f360aabf2b8a5691c550e1749dc41eb ]

The sun8i thermal driver reads calibration data via the nvmem API at
startup, updating the device configuration and not referencing the data
again.  Rather than explicitly freeing the nvmem data the driver relies
on devm_ to release it, even though the data is never referenced again.
The allocation is still tracked so it's not leaked but this is notable
when looking at the code and is a little wasteful so let's instead
explicitly free the nvmem after we're done with it.

Signed-off-by: Mark Brown <broonie@kernel.org>
Acked-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20230719-thermal-sun8i-free-nvmem-v1-1-f553d5afef79@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/thermal/sun8i_thermal.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/thermal/sun8i_thermal.c b/drivers/thermal/sun8i_thermal.c
index 80614b6adfac5..5776ecc8d0c76 100644
--- a/drivers/thermal/sun8i_thermal.c
+++ b/drivers/thermal/sun8i_thermal.c
@@ -286,7 +286,7 @@ static int sun8i_ths_calibrate(struct ths_device *tmdev)
 	size_t callen;
 	int ret = 0;
 
-	calcell = devm_nvmem_cell_get(dev, "calibration");
+	calcell = nvmem_cell_get(dev, "calibration");
 	if (IS_ERR(calcell)) {
 		if (PTR_ERR(calcell) == -EPROBE_DEFER)
 			return -EPROBE_DEFER;
@@ -316,6 +316,8 @@ static int sun8i_ths_calibrate(struct ths_device *tmdev)
 
 	kfree(caldata);
 out:
+	if (!IS_ERR(calcell))
+		nvmem_cell_put(calcell);
 	return ret;
 }
 
-- 
2.40.1