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-rw-r--r--debian/patches-rt/0112-printk-nbcon-Add-unsafe-flushing-on-panic.patch96
1 files changed, 96 insertions, 0 deletions
diff --git a/debian/patches-rt/0112-printk-nbcon-Add-unsafe-flushing-on-panic.patch b/debian/patches-rt/0112-printk-nbcon-Add-unsafe-flushing-on-panic.patch
new file mode 100644
index 0000000000..cc689de08e
--- /dev/null
+++ b/debian/patches-rt/0112-printk-nbcon-Add-unsafe-flushing-on-panic.patch
@@ -0,0 +1,96 @@
+From: John Ogness <john.ogness@linutronix.de>
+Date: Fri, 20 Oct 2023 10:03:42 +0000
+Subject: [PATCH 112/134] printk: nbcon: Add unsafe flushing on panic
+Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.6/older/patches-6.6.7-rt18.tar.xz
+
+Add nbcon_atomic_flush_unsafe() to flush all nbcon consoles
+using the write_atomic() callback and allowing unsafe hostile
+takeovers. Call this at the end of panic() as a final attempt
+to flush any pending messages.
+
+Note that legacy consoles use unsafe methods for flushing
+from the beginning of panic (see bust_spinlocks()). Therefore,
+systems using both legacy and nbcon consoles may still fail to
+see panic messages due to unsafe legacy console usage.
+
+Signed-off-by: John Ogness <john.ogness@linutronix.de>
+Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+---
+ include/linux/printk.h | 5 +++++
+ kernel/panic.c | 1 +
+ kernel/printk/nbcon.c | 18 ++++++++++++++++--
+ 3 files changed, 22 insertions(+), 2 deletions(-)
+
+--- a/include/linux/printk.h
++++ b/include/linux/printk.h
+@@ -199,6 +199,7 @@ extern asmlinkage void dump_stack(void)
+ void printk_trigger_flush(void);
+ extern void nbcon_acquire(struct uart_port *up);
+ extern void nbcon_release(struct uart_port *up);
++void nbcon_atomic_flush_unsafe(void);
+ #else
+ static inline __printf(1, 0)
+ int vprintk(const char *s, va_list args)
+@@ -287,6 +288,10 @@ static inline void nbcon_release(struct
+ {
+ }
+
++static inline void nbcon_atomic_flush_unsafe(void)
++{
++}
++
+ #endif
+
+ #ifdef CONFIG_SMP
+--- a/kernel/panic.c
++++ b/kernel/panic.c
+@@ -449,6 +449,7 @@ void panic(const char *fmt, ...)
+ * Explicitly flush the kernel log buffer one last time.
+ */
+ console_flush_on_panic(CONSOLE_FLUSH_PENDING);
++ nbcon_atomic_flush_unsafe();
+
+ local_irq_enable();
+ for (i = 0; ; i += PANIC_TIMER_STEP) {
+--- a/kernel/printk/nbcon.c
++++ b/kernel/printk/nbcon.c
+@@ -1030,8 +1030,9 @@ bool nbcon_atomic_emit_next_record(struc
+ * __nbcon_atomic_flush_all - Flush all nbcon consoles using their
+ * write_atomic() callback
+ * @stop_seq: Flush up until this record
++ * @allow_unsafe_takeover: True, to allow unsafe hostile takeovers
+ */
+-static void __nbcon_atomic_flush_all(u64 stop_seq)
++static void __nbcon_atomic_flush_all(u64 stop_seq, bool allow_unsafe_takeover)
+ {
+ struct nbcon_write_context wctxt = { };
+ struct nbcon_context *ctxt = &ACCESS_PRIVATE(&wctxt, ctxt);
+@@ -1059,6 +1060,7 @@ static void __nbcon_atomic_flush_all(u64
+ memset(ctxt, 0, sizeof(*ctxt));
+ ctxt->console = con;
+ ctxt->spinwait_max_us = 2000;
++ ctxt->allow_unsafe_takeover = allow_unsafe_takeover;
+
+ /*
+ * Atomic flushing does not use console driver
+@@ -1093,7 +1095,19 @@ static void __nbcon_atomic_flush_all(u64
+ */
+ void nbcon_atomic_flush_all(void)
+ {
+- __nbcon_atomic_flush_all(prb_next_reserve_seq(prb));
++ __nbcon_atomic_flush_all(prb_next_reserve_seq(prb), false);
++}
++
++/**
++ * nbcon_atomic_flush_unsafe - Flush all nbcon consoles using their
++ * write_atomic() callback and allowing unsafe hostile takeovers
++ *
++ * Flush the backlog up through the currently newest record. Unsafe hostile
++ * takeovers will be performed, if necessary.
++ */
++void nbcon_atomic_flush_unsafe(void)
++{
++ __nbcon_atomic_flush_all(prb_next_reserve_seq(prb), true);
+ }
+
+ /**