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-rw-r--r--debian/patches-rt/0082-printk-nbcon-Allow-drivers-to-mark-unsafe-regions-an.patch136
1 files changed, 136 insertions, 0 deletions
diff --git a/debian/patches-rt/0082-printk-nbcon-Allow-drivers-to-mark-unsafe-regions-an.patch b/debian/patches-rt/0082-printk-nbcon-Allow-drivers-to-mark-unsafe-regions-an.patch
new file mode 100644
index 0000000000..16a07a839e
--- /dev/null
+++ b/debian/patches-rt/0082-printk-nbcon-Allow-drivers-to-mark-unsafe-regions-an.patch
@@ -0,0 +1,136 @@
+From: Thomas Gleixner <tglx@linutronix.de>
+Date: Sat, 16 Sep 2023 21:26:07 +0206
+Subject: [PATCH 082/134] printk: nbcon: Allow drivers to mark unsafe regions
+ and check state
+Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.6/older/patches-6.6.7-rt18.tar.xz
+
+For the write_atomic callback, the console driver may have unsafe
+regions that need to be appropriately marked. Provide functions
+that accept the nbcon_write_context struct to allow for the driver
+to enter and exit unsafe regions.
+
+Also provide a function for drivers to check if they are still the
+owner of the console.
+
+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>
+Reviewed-by: Petr Mladek <pmladek@suse.com>
+Signed-off-by: Petr Mladek <pmladek@suse.com>
+Link: https://lore.kernel.org/r/20230916192007.608398-9-john.ogness@linutronix.de
+Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+---
+ include/linux/console.h | 10 ++++++
+ kernel/printk/nbcon.c | 75 ++++++++++++++++++++++++++++++++++++++++++++++++
+ 2 files changed, 85 insertions(+)
+
+--- a/include/linux/console.h
++++ b/include/linux/console.h
+@@ -451,6 +451,16 @@ static inline bool console_is_registered
+ lockdep_assert_console_list_lock_held(); \
+ hlist_for_each_entry(con, &console_list, node)
+
++#ifdef CONFIG_PRINTK
++extern bool nbcon_can_proceed(struct nbcon_write_context *wctxt);
++extern bool nbcon_enter_unsafe(struct nbcon_write_context *wctxt);
++extern bool nbcon_exit_unsafe(struct nbcon_write_context *wctxt);
++#else
++static inline bool nbcon_can_proceed(struct nbcon_write_context *wctxt) { return false; }
++static inline bool nbcon_enter_unsafe(struct nbcon_write_context *wctxt) { return false; }
++static inline bool nbcon_exit_unsafe(struct nbcon_write_context *wctxt) { return false; }
++#endif
++
+ extern int console_set_on_cmdline;
+ extern struct console *early_console;
+
+--- a/kernel/printk/nbcon.c
++++ b/kernel/printk/nbcon.c
+@@ -732,6 +732,41 @@ static bool nbcon_context_can_proceed(st
+ return false;
+ }
+
++/**
++ * nbcon_can_proceed - Check whether ownership can proceed
++ * @wctxt: The write context that was handed to the write function
++ *
++ * Return: True if this context still owns the console. False if
++ * ownership was handed over or taken.
++ *
++ * It is used in nbcon_enter_unsafe() to make sure that it still owns the
++ * lock. Also it is used in nbcon_exit_unsafe() to eventually free the lock
++ * for a higher priority context which asked for the friendly handover.
++ *
++ * It can be called inside an unsafe section when the console is just
++ * temporary in safe state instead of exiting and entering the unsafe state.
++ *
++ * Also it can be called in the safe context before doing an expensive safe
++ * operation. It does not make sense to do the operation when a higher
++ * priority context took the lock.
++ *
++ * When this function returns false then the calling context no longer owns
++ * the console and is no longer allowed to go forward. In this case it must
++ * back out immediately and carefully. The buffer content is also no longer
++ * trusted since it no longer belongs to the calling context.
++ */
++bool nbcon_can_proceed(struct nbcon_write_context *wctxt)
++{
++ struct nbcon_context *ctxt = &ACCESS_PRIVATE(wctxt, ctxt);
++ struct console *con = ctxt->console;
++ struct nbcon_state cur;
++
++ nbcon_state_read(con, &cur);
++
++ return nbcon_context_can_proceed(ctxt, &cur);
++}
++EXPORT_SYMBOL_GPL(nbcon_can_proceed);
++
+ #define nbcon_context_enter_unsafe(c) __nbcon_context_update_unsafe(c, true)
+ #define nbcon_context_exit_unsafe(c) __nbcon_context_update_unsafe(c, false)
+
+@@ -783,6 +818,46 @@ static bool __nbcon_context_update_unsaf
+ }
+
+ /**
++ * nbcon_enter_unsafe - Enter an unsafe region in the driver
++ * @wctxt: The write context that was handed to the write function
++ *
++ * Return: True if this context still owns the console. False if
++ * ownership was handed over or taken.
++ *
++ * When this function returns false then the calling context no longer owns
++ * the console and is no longer allowed to go forward. In this case it must
++ * back out immediately and carefully. The buffer content is also no longer
++ * trusted since it no longer belongs to the calling context.
++ */
++bool nbcon_enter_unsafe(struct nbcon_write_context *wctxt)
++{
++ struct nbcon_context *ctxt = &ACCESS_PRIVATE(wctxt, ctxt);
++
++ return nbcon_context_enter_unsafe(ctxt);
++}
++EXPORT_SYMBOL_GPL(nbcon_enter_unsafe);
++
++/**
++ * nbcon_exit_unsafe - Exit an unsafe region in the driver
++ * @wctxt: The write context that was handed to the write function
++ *
++ * Return: True if this context still owns the console. False if
++ * ownership was handed over or taken.
++ *
++ * When this function returns false then the calling context no longer owns
++ * the console and is no longer allowed to go forward. In this case it must
++ * back out immediately and carefully. The buffer content is also no longer
++ * trusted since it no longer belongs to the calling context.
++ */
++bool nbcon_exit_unsafe(struct nbcon_write_context *wctxt)
++{
++ struct nbcon_context *ctxt = &ACCESS_PRIVATE(wctxt, ctxt);
++
++ return nbcon_context_exit_unsafe(ctxt);
++}
++EXPORT_SYMBOL_GPL(nbcon_exit_unsafe);
++
++/**
+ * nbcon_emit_next_record - Emit a record in the acquired context
+ * @wctxt: The write context that will be handed to the write function
+ *