diff options
Diffstat (limited to 'debian/patches-rt/0020-printk-nbcon-Provide-function-to-flush-using-write_a.patch')
| -rw-r--r-- | debian/patches-rt/0020-printk-nbcon-Provide-function-to-flush-using-write_a.patch | 193 |
1 files changed, 0 insertions, 193 deletions
diff --git a/debian/patches-rt/0020-printk-nbcon-Provide-function-to-flush-using-write_a.patch b/debian/patches-rt/0020-printk-nbcon-Provide-function-to-flush-using-write_a.patch deleted file mode 100644 index 26c68ed22..000000000 --- a/debian/patches-rt/0020-printk-nbcon-Provide-function-to-flush-using-write_a.patch +++ /dev/null @@ -1,193 +0,0 @@ -From: Thomas Gleixner <tglx@linutronix.de> -Date: Tue, 12 Sep 2023 12:00:08 +0000 -Subject: [PATCH 20/48] printk: nbcon: Provide function to flush using - write_atomic() -Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.8/older/patches-6.8.2-rt11.tar.xz - -Provide nbcon_atomic_flush_pending() to perform flushing of all -registered nbcon consoles using their write_atomic() callback. - -Unlike console_flush_all(), nbcon_atomic_flush_pending() will -only flush up through the newest record at the time of the -call. This prevents a CPU from printing unbounded when other -CPUs are adding records. - -Also unlike console_flush_all(), nbcon_atomic_flush_pending() -will fully flush one console before flushing the next. This -helps to guarantee that a block of pending records (such as -a stack trace in an emergency situation) can be printed -atomically at once before releasing console ownership. - -nbcon_atomic_flush_pending() is safe in any context because it -uses write_atomic() and acquires with unsafe_takeover disabled. - -Use it in console_flush_on_panic() before flushing legacy -consoles. The legacy write() callbacks are not fully safe when -oops_in_progress is set. - -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> ---- - kernel/printk/internal.h | 2 - kernel/printk/nbcon.c | 104 ++++++++++++++++++++++++++++++++++++++++++++++- - kernel/printk/printk.c | 2 - 3 files changed, 106 insertions(+), 2 deletions(-) - ---- a/kernel/printk/internal.h -+++ b/kernel/printk/internal.h -@@ -84,6 +84,7 @@ void nbcon_seq_force(struct console *con - bool nbcon_alloc(struct console *con); - void nbcon_init(struct console *con); - void nbcon_free(struct console *con); -+void nbcon_atomic_flush_pending(void); - - /* - * Check if the given console is currently capable and allowed to print -@@ -138,6 +139,7 @@ static inline void nbcon_seq_force(struc - static inline bool nbcon_alloc(struct console *con) { return false; } - static inline void nbcon_init(struct console *con) { } - static inline void nbcon_free(struct console *con) { } -+static inline void nbcon_atomic_flush_pending(void) { } - - static inline bool console_is_usable(struct console *con, short flags) { return false; } - ---- a/kernel/printk/nbcon.c -+++ b/kernel/printk/nbcon.c -@@ -548,7 +548,6 @@ static struct printk_buffers panic_nbcon - * in an unsafe state. Otherwise, on success the caller may assume - * the console is not in an unsafe state. - */ --__maybe_unused - static bool nbcon_context_try_acquire(struct nbcon_context *ctxt) - { - unsigned int cpu = smp_processor_id(); -@@ -850,7 +849,6 @@ EXPORT_SYMBOL_GPL(nbcon_exit_unsafe); - * When true is returned, @wctxt->ctxt.backlog indicates whether there are - * still records pending in the ringbuffer, - */ --__maybe_unused - static bool nbcon_emit_next_record(struct nbcon_write_context *wctxt) - { - struct nbcon_context *ctxt = &ACCESS_PRIVATE(wctxt, ctxt); -@@ -938,6 +936,108 @@ static bool nbcon_emit_next_record(struc - } - - /** -+ * __nbcon_atomic_flush_pending_con - Flush specified nbcon console using its -+ * write_atomic() callback -+ * @con: The nbcon console to flush -+ * @stop_seq: Flush up until this record -+ * -+ * Return: True if taken over while printing. Otherwise false. -+ * -+ * If flushing up to @stop_seq was not successful, it only makes sense for the -+ * caller to try again when true was returned. When false is returned, either -+ * there are no more records available to read or this context is not allowed -+ * to acquire the console. -+ */ -+static bool __nbcon_atomic_flush_pending_con(struct console *con, u64 stop_seq) -+{ -+ struct nbcon_write_context wctxt = { }; -+ struct nbcon_context *ctxt = &ACCESS_PRIVATE(&wctxt, ctxt); -+ -+ ctxt->console = con; -+ ctxt->spinwait_max_us = 2000; -+ ctxt->prio = NBCON_PRIO_NORMAL; -+ -+ if (!nbcon_context_try_acquire(ctxt)) -+ return false; -+ -+ while (nbcon_seq_read(con) < stop_seq) { -+ /* -+ * nbcon_emit_next_record() returns false when the console was -+ * handed over or taken over. In both cases the context is no -+ * longer valid. -+ */ -+ if (!nbcon_emit_next_record(&wctxt)) -+ return true; -+ -+ if (!ctxt->backlog) -+ break; -+ } -+ -+ nbcon_context_release(ctxt); -+ -+ return false; -+} -+ -+/** -+ * __nbcon_atomic_flush_pending - Flush all nbcon consoles using their -+ * write_atomic() callback -+ * @stop_seq: Flush up until this record -+ */ -+static void __nbcon_atomic_flush_pending(u64 stop_seq) -+{ -+ struct console *con; -+ bool should_retry; -+ int cookie; -+ -+ do { -+ should_retry = false; -+ -+ cookie = console_srcu_read_lock(); -+ for_each_console_srcu(con) { -+ short flags = console_srcu_read_flags(con); -+ unsigned long irq_flags; -+ -+ if (!(flags & CON_NBCON)) -+ continue; -+ -+ if (!console_is_usable(con, flags)) -+ continue; -+ -+ if (nbcon_seq_read(con) >= stop_seq) -+ continue; -+ -+ /* -+ * Atomic flushing does not use console driver -+ * synchronization (i.e. it does not hold the port -+ * lock for uart consoles). Therefore IRQs must be -+ * disabled to avoid being interrupted and then -+ * calling into a driver that will deadlock trying -+ * to acquire console ownership. -+ */ -+ local_irq_save(irq_flags); -+ -+ should_retry |= __nbcon_atomic_flush_pending_con(con, stop_seq); -+ -+ local_irq_restore(irq_flags); -+ } -+ console_srcu_read_unlock(cookie); -+ } while (should_retry); -+} -+ -+/** -+ * nbcon_atomic_flush_pending - Flush all nbcon consoles using their -+ * write_atomic() callback -+ * -+ * Flush the backlog up through the currently newest record. Any new -+ * records added while flushing will not be flushed. This is to avoid -+ * one CPU printing unbounded because other CPUs continue to add records. -+ */ -+void nbcon_atomic_flush_pending(void) -+{ -+ __nbcon_atomic_flush_pending(prb_next_reserve_seq(prb)); -+} -+ -+/** - * nbcon_alloc - Allocate buffers needed by the nbcon console - * @con: Console to allocate buffers for - * ---- a/kernel/printk/printk.c -+++ b/kernel/printk/printk.c -@@ -3177,6 +3177,8 @@ void console_flush_on_panic(enum con_flu - console_srcu_read_unlock(cookie); - } - -+ nbcon_atomic_flush_pending(); -+ - console_flush_all(false, &next_seq, &handover); - } - |