diff options
Diffstat (limited to '')
| -rw-r--r-- | debian/patches-rt/0081-printk-nbcon-Add-emit-function-and-callback-function.patch | 262 |
1 files changed, 262 insertions, 0 deletions
diff --git a/debian/patches-rt/0081-printk-nbcon-Add-emit-function-and-callback-function.patch b/debian/patches-rt/0081-printk-nbcon-Add-emit-function-and-callback-function.patch new file mode 100644 index 000000000..ab32a05b1 --- /dev/null +++ b/debian/patches-rt/0081-printk-nbcon-Add-emit-function-and-callback-function.patch @@ -0,0 +1,262 @@ +From: Thomas Gleixner <tglx@linutronix.de> +Date: Sat, 16 Sep 2023 21:26:06 +0206 +Subject: [PATCH 081/134] printk: nbcon: Add emit function and callback + function for atomic printing +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.6/older/patches-6.6.7-rt18.tar.xz + +Implement an emit function for nbcon consoles to output printk +messages. It utilizes the lockless printk_get_next_message() and +console_prepend_dropped() functions to retrieve/build the output +message. The emit function includes the required safety points to +check for handover/takeover and calls a new write_atomic callback +of the console driver to output the message. It also includes +proper handling for updating the nbcon console sequence number. + +A new nbcon_write_context struct is introduced. This is provided +to the write_atomic callback and includes only the information +necessary for performing atomic writes. + +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/20230916192007.608398-8-john.ogness@linutronix.de +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + include/linux/console.h | 21 +++++++++ + kernel/printk/internal.h | 6 ++ + kernel/printk/nbcon.c | 106 ++++++++++++++++++++++++++++++++++++++++++++++- + kernel/printk/printk.c | 9 +-- + 4 files changed, 134 insertions(+), 8 deletions(-) + +--- a/include/linux/console.h ++++ b/include/linux/console.h +@@ -242,6 +242,7 @@ struct printk_buffers; + * be used only with NBCON_PRIO_PANIC @prio. It + * might cause a system freeze when the console + * is used later. ++ * @backlog: Ringbuffer has pending records + * @pbufs: Pointer to the text buffer for this context + * @seq: The sequence number to print for this context + */ +@@ -252,12 +253,29 @@ struct nbcon_context { + enum nbcon_prio prio; + unsigned int allow_unsafe_takeover : 1; + ++ /* members set by emit */ ++ unsigned int backlog : 1; ++ + /* members set by acquire */ + struct printk_buffers *pbufs; + u64 seq; + }; + + /** ++ * struct nbcon_write_context - Context handed to the nbcon write callbacks ++ * @ctxt: The core console context ++ * @outbuf: Pointer to the text buffer for output ++ * @len: Length to write ++ * @unsafe_takeover: If a hostile takeover in an unsafe state has occurred ++ */ ++struct nbcon_write_context { ++ struct nbcon_context __private ctxt; ++ char *outbuf; ++ unsigned int len; ++ bool unsafe_takeover; ++}; ++ ++/** + * struct console - The console descriptor structure + * @name: The name of the console driver + * @write: Write callback to output messages (Optional) +@@ -277,6 +295,7 @@ struct nbcon_context { + * @data: Driver private data + * @node: hlist node for the console list + * ++ * @write_atomic: Write callback for atomic context + * @nbcon_state: State for nbcon consoles + * @nbcon_seq: Sequence number of the next record for nbcon to print + * @pbufs: Pointer to nbcon private buffer +@@ -301,6 +320,8 @@ struct console { + struct hlist_node node; + + /* nbcon console specific members */ ++ bool (*write_atomic)(struct console *con, ++ struct nbcon_write_context *wctxt); + atomic_t __private nbcon_state; + atomic_long_t __private nbcon_seq; + struct printk_buffers *pbufs; +--- a/kernel/printk/internal.h ++++ b/kernel/printk/internal.h +@@ -130,3 +130,9 @@ struct printk_message { + }; + + bool other_cpu_in_panic(void); ++bool printk_get_next_message(struct printk_message *pmsg, u64 seq, ++ bool is_extended, bool may_supress); ++ ++#ifdef CONFIG_PRINTK ++void console_prepend_dropped(struct printk_message *pmsg, unsigned long dropped); ++#endif +--- a/kernel/printk/nbcon.c ++++ b/kernel/printk/nbcon.c +@@ -221,7 +221,6 @@ void nbcon_seq_force(struct console *con + * nbcon_seq_force() was used or the current context no longer owns the + * console. In the later case, it will stop printing anyway. + */ +-__maybe_unused + static void nbcon_seq_try_update(struct nbcon_context *ctxt, u64 new_seq) + { + unsigned long nbcon_seq = __seq_to_nbcon_seq(ctxt->seq); +@@ -755,7 +754,6 @@ static bool nbcon_context_can_proceed(st + * + * Internal helper to avoid duplicated code. + */ +-__maybe_unused + static bool __nbcon_context_update_unsafe(struct nbcon_context *ctxt, bool unsafe) + { + struct console *con = ctxt->console; +@@ -785,6 +783,110 @@ static bool __nbcon_context_update_unsaf + } + + /** ++ * nbcon_emit_next_record - Emit a record in the acquired context ++ * @wctxt: The write context that will be 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. If the caller ++ * wants to do more it must reacquire the console first. ++ * ++ * 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); ++ struct console *con = ctxt->console; ++ bool is_extended = console_srcu_read_flags(con) & CON_EXTENDED; ++ struct printk_message pmsg = { ++ .pbufs = ctxt->pbufs, ++ }; ++ unsigned long con_dropped; ++ struct nbcon_state cur; ++ unsigned long dropped; ++ bool done; ++ ++ /* ++ * The printk buffers are filled within an unsafe section. This ++ * prevents NBCON_PRIO_NORMAL and NBCON_PRIO_EMERGENCY from ++ * clobbering each other. ++ */ ++ ++ if (!nbcon_context_enter_unsafe(ctxt)) ++ return false; ++ ++ ctxt->backlog = printk_get_next_message(&pmsg, ctxt->seq, is_extended, true); ++ if (!ctxt->backlog) ++ return nbcon_context_exit_unsafe(ctxt); ++ ++ /* ++ * @con->dropped is not protected in case of an unsafe hostile ++ * takeover. In that situation the update can be racy so ++ * annotate it accordingly. ++ */ ++ con_dropped = data_race(READ_ONCE(con->dropped)); ++ ++ dropped = con_dropped + pmsg.dropped; ++ if (dropped && !is_extended) ++ console_prepend_dropped(&pmsg, dropped); ++ ++ if (!nbcon_context_exit_unsafe(ctxt)) ++ return false; ++ ++ /* For skipped records just update seq/dropped in @con. */ ++ if (pmsg.outbuf_len == 0) ++ goto update_con; ++ ++ /* Initialize the write context for driver callbacks. */ ++ wctxt->outbuf = &pmsg.pbufs->outbuf[0]; ++ wctxt->len = pmsg.outbuf_len; ++ nbcon_state_read(con, &cur); ++ wctxt->unsafe_takeover = cur.unsafe_takeover; ++ ++ if (con->write_atomic) { ++ done = con->write_atomic(con, wctxt); ++ } else { ++ nbcon_context_release(ctxt); ++ WARN_ON_ONCE(1); ++ done = false; ++ } ++ ++ /* If not done, the emit was aborted. */ ++ if (!done) ++ return false; ++ ++ /* ++ * Since any dropped message was successfully output, reset the ++ * dropped count for the console. ++ */ ++ dropped = 0; ++update_con: ++ /* ++ * The dropped count and the sequence number are updated within an ++ * unsafe section. This limits update races to the panic context and ++ * allows the panic context to win. ++ */ ++ ++ if (!nbcon_context_enter_unsafe(ctxt)) ++ return false; ++ ++ if (dropped != con_dropped) { ++ /* Counterpart to the READ_ONCE() above. */ ++ WRITE_ONCE(con->dropped, dropped); ++ } ++ ++ nbcon_seq_try_update(ctxt, pmsg.seq + 1); ++ ++ return nbcon_context_exit_unsafe(ctxt); ++} ++ ++/** + * 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 +@@ -698,9 +698,6 @@ static ssize_t msg_print_ext_body(char * + return len; + } + +-static bool printk_get_next_message(struct printk_message *pmsg, u64 seq, +- bool is_extended, bool may_supress); +- + /* /dev/kmsg - userspace message inject/listen interface */ + struct devkmsg_user { + atomic64_t seq; +@@ -2733,7 +2730,7 @@ static void __console_unlock(void) + * If @pmsg->pbufs->outbuf is modified, @pmsg->outbuf_len is updated. + */ + #ifdef CONFIG_PRINTK +-static void console_prepend_dropped(struct printk_message *pmsg, unsigned long dropped) ++void console_prepend_dropped(struct printk_message *pmsg, unsigned long dropped) + { + struct printk_buffers *pbufs = pmsg->pbufs; + const size_t scratchbuf_sz = sizeof(pbufs->scratchbuf); +@@ -2787,8 +2784,8 @@ static void console_prepend_dropped(stru + * of @pmsg are valid. (See the documentation of struct printk_message + * for information about the @pmsg fields.) + */ +-static bool printk_get_next_message(struct printk_message *pmsg, u64 seq, +- bool is_extended, bool may_suppress) ++bool printk_get_next_message(struct printk_message *pmsg, u64 seq, ++ bool is_extended, bool may_suppress) + { + static int panic_console_dropped; + |