176 lines
5.2 KiB
Diff
176 lines
5.2 KiB
Diff
From c643ed9ef56cd3a3b7c97bdd573392c4983b8ee1 Mon Sep 17 00:00:00 2001
|
|
From: Thomas Gleixner <tglx@linutronix.de>
|
|
Date: Tue, 26 Sep 2023 13:03:52 +0000
|
|
Subject: [PATCH 150/196] printk: nbcon: Add printer thread wakeups
|
|
|
|
Add a function to wakeup the printer threads. Use the new function
|
|
when:
|
|
|
|
- records are added to the printk ringbuffer
|
|
- consoles are resumed
|
|
- triggered via printk_trigger_flush()
|
|
|
|
The actual waking is performed via irq_work so that the wakeup can
|
|
be triggered from any context.
|
|
|
|
Co-developed-by: John Ogness <john.ogness@linutronix.de>
|
|
Signed-off-by: John Ogness <john.ogness@linutronix.de>
|
|
Signed-off-by: Thomas Gleixner (Intel) <tglx@linutronix.de>
|
|
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
|
|
---
|
|
include/linux/console.h | 3 +++
|
|
kernel/printk/internal.h | 1 +
|
|
kernel/printk/nbcon.c | 56 ++++++++++++++++++++++++++++++++++++++++
|
|
kernel/printk/printk.c | 7 +++++
|
|
4 files changed, 67 insertions(+)
|
|
|
|
diff --git a/include/linux/console.h b/include/linux/console.h
|
|
index 5b5333faac7a..982c98280ae8 100644
|
|
--- a/include/linux/console.h
|
|
+++ b/include/linux/console.h
|
|
@@ -16,6 +16,7 @@
|
|
|
|
#include <linux/atomic.h>
|
|
#include <linux/bits.h>
|
|
+#include <linux/irq_work.h>
|
|
#include <linux/rculist.h>
|
|
#include <linux/rcuwait.h>
|
|
#include <linux/types.h>
|
|
@@ -306,6 +307,7 @@ struct nbcon_write_context {
|
|
* @locked_port: True, if the port lock is locked by nbcon
|
|
* @kthread: Printer kthread for this console
|
|
* @rcuwait: RCU-safe wait object for @kthread waking
|
|
+ * @irq_work: Defer @kthread waking to IRQ work context
|
|
*/
|
|
struct console {
|
|
char name[16];
|
|
@@ -339,6 +341,7 @@ struct console {
|
|
bool locked_port;
|
|
struct task_struct *kthread;
|
|
struct rcuwait rcuwait;
|
|
+ struct irq_work irq_work;
|
|
};
|
|
|
|
#ifdef CONFIG_LOCKDEP
|
|
diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h
|
|
index e5eb7dc25e0a..578623e7f0fc 100644
|
|
--- a/kernel/printk/internal.h
|
|
+++ b/kernel/printk/internal.h
|
|
@@ -93,6 +93,7 @@ enum nbcon_prio nbcon_get_default_prio(void);
|
|
void nbcon_atomic_flush_all(void);
|
|
bool nbcon_atomic_emit_next_record(struct console *con, bool *handover, int cookie);
|
|
void nbcon_kthread_create(struct console *con);
|
|
+void nbcon_wake_threads(void);
|
|
|
|
/*
|
|
* Check if the given console is currently capable and allowed to print
|
|
diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c
|
|
index bb071193ab6e..337ec7a10095 100644
|
|
--- a/kernel/printk/nbcon.c
|
|
+++ b/kernel/printk/nbcon.c
|
|
@@ -1052,6 +1052,61 @@ static int nbcon_kthread_func(void *__console)
|
|
goto wait_for_event;
|
|
}
|
|
|
|
+/**
|
|
+ * nbcon_irq_work - irq work to wake printk thread
|
|
+ * @irq_work: The irq work to operate on
|
|
+ */
|
|
+static void nbcon_irq_work(struct irq_work *irq_work)
|
|
+{
|
|
+ struct console *con = container_of(irq_work, struct console, irq_work);
|
|
+
|
|
+ nbcon_kthread_wake(con);
|
|
+}
|
|
+
|
|
+static inline bool rcuwait_has_sleeper(struct rcuwait *w)
|
|
+{
|
|
+ bool has_sleeper;
|
|
+
|
|
+ rcu_read_lock();
|
|
+ /*
|
|
+ * Guarantee any new records can be seen by tasks preparing to wait
|
|
+ * before this context checks if the rcuwait is empty.
|
|
+ *
|
|
+ * This full memory barrier pairs with the full memory barrier within
|
|
+ * set_current_state() of ___rcuwait_wait_event(), which is called
|
|
+ * after prepare_to_rcuwait() adds the waiter but before it has
|
|
+ * checked the wait condition.
|
|
+ *
|
|
+ * This pairs with nbcon_kthread_func:A.
|
|
+ */
|
|
+ smp_mb(); /* LMM(rcuwait_has_sleeper:A) */
|
|
+ has_sleeper = !!rcu_dereference(w->task);
|
|
+ rcu_read_unlock();
|
|
+
|
|
+ return has_sleeper;
|
|
+}
|
|
+
|
|
+/**
|
|
+ * nbcon_wake_threads - Wake up printing threads using irq_work
|
|
+ */
|
|
+void nbcon_wake_threads(void)
|
|
+{
|
|
+ struct console *con;
|
|
+ int cookie;
|
|
+
|
|
+ cookie = console_srcu_read_lock();
|
|
+ for_each_console_srcu(con) {
|
|
+ /*
|
|
+ * Only schedule irq_work if the printing thread is
|
|
+ * actively waiting. If not waiting, the thread will
|
|
+ * notice by itself that it has work to do.
|
|
+ */
|
|
+ if (con->kthread && rcuwait_has_sleeper(&con->rcuwait))
|
|
+ irq_work_queue(&con->irq_work);
|
|
+ }
|
|
+ console_srcu_read_unlock(cookie);
|
|
+}
|
|
+
|
|
/* Track the nbcon emergency nesting per CPU. */
|
|
static DEFINE_PER_CPU(unsigned int, nbcon_pcpu_emergency_nesting);
|
|
static unsigned int early_nbcon_pcpu_emergency_nesting __initdata;
|
|
@@ -1418,6 +1473,7 @@ void nbcon_init(struct console *con)
|
|
BUG_ON(!con->pbufs);
|
|
|
|
rcuwait_init(&con->rcuwait);
|
|
+ init_irq_work(&con->irq_work, nbcon_irq_work);
|
|
nbcon_seq_force(con, con->seq);
|
|
nbcon_state_set(con, &state);
|
|
}
|
|
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
|
|
index f11381f39c98..41370f284216 100644
|
|
--- a/kernel/printk/printk.c
|
|
+++ b/kernel/printk/printk.c
|
|
@@ -2403,6 +2403,8 @@ asmlinkage int vprintk_emit(int facility, int level,
|
|
}
|
|
}
|
|
|
|
+ nbcon_wake_threads();
|
|
+
|
|
if (do_trylock_unlock) {
|
|
/*
|
|
* The caller may be holding system-critical or
|
|
@@ -2705,6 +2707,10 @@ void resume_console(void)
|
|
*/
|
|
synchronize_srcu(&console_srcu);
|
|
|
|
+ /*
|
|
+ * Since this runs in task context, wake the threaded printers
|
|
+ * directly rather than scheduling irq_work to do it.
|
|
+ */
|
|
cookie = console_srcu_read_lock();
|
|
for_each_console_srcu(con) {
|
|
flags = console_srcu_read_flags(con);
|
|
@@ -4097,6 +4103,7 @@ void defer_console_output(void)
|
|
|
|
void printk_trigger_flush(void)
|
|
{
|
|
+ nbcon_wake_threads();
|
|
defer_console_output();
|
|
}
|
|
|
|
--
|
|
2.43.2
|
|
|