diff options
Diffstat (limited to 'debian/patches-rt/0040-printk-nbcon-Add-printer-thread-wakeups.patch')
| -rw-r--r-- | debian/patches-rt/0040-printk-nbcon-Add-printer-thread-wakeups.patch | 164 |
1 files changed, 164 insertions, 0 deletions
diff --git a/debian/patches-rt/0040-printk-nbcon-Add-printer-thread-wakeups.patch b/debian/patches-rt/0040-printk-nbcon-Add-printer-thread-wakeups.patch new file mode 100644 index 0000000000..89e086aa32 --- /dev/null +++ b/debian/patches-rt/0040-printk-nbcon-Add-printer-thread-wakeups.patch @@ -0,0 +1,164 @@ +From: Thomas Gleixner <tglx@linutronix.de> +Date: Tue, 26 Sep 2023 13:03:52 +0000 +Subject: [PATCH 40/50] printk: nbcon: Add printer thread wakeups +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.7/older/patches-6.7-rt6.tar.xz + +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(+) + +--- 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> +@@ -313,6 +314,7 @@ 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]; +@@ -346,6 +348,7 @@ struct console { + bool locked_port; + struct task_struct *kthread; + struct rcuwait rcuwait; ++ struct irq_work irq_work; + }; + + #ifdef CONFIG_LOCKDEP +--- a/kernel/printk/internal.h ++++ b/kernel/printk/internal.h +@@ -93,6 +93,7 @@ enum nbcon_prio nbcon_get_default_prio(v + 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 +--- a/kernel/printk/nbcon.c ++++ b/kernel/printk/nbcon.c +@@ -1052,6 +1052,61 @@ static int nbcon_kthread_func(void *__co + 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); + } +--- a/kernel/printk/printk.c ++++ b/kernel/printk/printk.c +@@ -2402,6 +2402,8 @@ asmlinkage int vprintk_emit(int facility + } + } + ++ nbcon_wake_threads(); ++ + if (do_trylock_unlock) { + /* + * The caller may be holding system-critical or +@@ -2712,6 +2714,10 @@ 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); +@@ -4104,6 +4110,7 @@ void defer_console_output(void) + + void printk_trigger_flush(void) + { ++ nbcon_wake_threads(); + defer_console_output(); + } + |