diff options
Diffstat (limited to '')
| -rw-r--r-- | debian/patches-rt/0079-printk-nbcon-Add-ownership-state-functions.patch | 179 |
1 files changed, 0 insertions, 179 deletions
diff --git a/debian/patches-rt/0079-printk-nbcon-Add-ownership-state-functions.patch b/debian/patches-rt/0079-printk-nbcon-Add-ownership-state-functions.patch deleted file mode 100644 index e26a5f332d..0000000000 --- a/debian/patches-rt/0079-printk-nbcon-Add-ownership-state-functions.patch +++ /dev/null @@ -1,179 +0,0 @@ -From: Thomas Gleixner <tglx@linutronix.de> -Date: Sat, 16 Sep 2023 21:26:04 +0206 -Subject: [PATCH 079/134] printk: nbcon: Add ownership state functions -Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.6/older/patches-6.6.7-rt18.tar.xz - -Provide functions that are related to the safe handover mechanism -and allow console drivers to dynamically specify unsafe regions: - - - nbcon_context_can_proceed() - - Invoked by a console owner to check whether a handover request - is pending or whether the console has been taken over by another - context. If a handover request is pending, this function will - also perform the handover, thus cancelling its own ownership. - - - nbcon_context_enter_unsafe()/nbcon_context_exit_unsafe() - - Invoked by a console owner to denote that the driver is about - to enter or leave a critical region where a take over is unsafe. - The exit variant is the point where the current owner releases - the lock for a higher priority context which asked for the - friendly handover. - - The unsafe state is stored in the console state and allows a - new context to make informed decisions whether to attempt a - takeover of such a console. The unsafe state is also available - to the driver so that it can make informed decisions about the - required actions and possibly take a special emergency path. - -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/20230916192007.608398-6-john.ogness@linutronix.de -Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> ---- - kernel/printk/nbcon.c | 123 +++++++++++++++++++++++++++++++++++++++++++++++++- - 1 file changed, 122 insertions(+), 1 deletion(-) - ---- a/kernel/printk/nbcon.c -+++ b/kernel/printk/nbcon.c -@@ -537,7 +537,6 @@ static bool nbcon_owner_matches(struct n - * nbcon_context_release - Release the console - * @ctxt: The nbcon context from nbcon_context_try_acquire() - */ --__maybe_unused - static void nbcon_context_release(struct nbcon_context *ctxt) - { - unsigned int cpu = smp_processor_id(); -@@ -566,6 +565,128 @@ static void nbcon_context_release(struct - } - - /** -+ * nbcon_context_can_proceed - Check whether ownership can proceed -+ * @ctxt: The nbcon context from nbcon_context_try_acquire() -+ * @cur: The current console state -+ * -+ * Return: True if this context still owns the console. False if -+ * ownership was handed over or taken. -+ * -+ * Must be invoked when entering the unsafe state to make sure that it still -+ * owns the lock. Also must be invoked when exiting the unsafe context -+ * 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. -+ */ -+static bool nbcon_context_can_proceed(struct nbcon_context *ctxt, struct nbcon_state *cur) -+{ -+ unsigned int cpu = smp_processor_id(); -+ -+ /* Make sure this context still owns the console. */ -+ if (!nbcon_owner_matches(cur, cpu, ctxt->prio)) -+ return false; -+ -+ /* The console owner can proceed if there is no waiter. */ -+ if (cur->req_prio == NBCON_PRIO_NONE) -+ return true; -+ -+ /* -+ * A console owner within an unsafe region is always allowed to -+ * proceed, even if there are waiters. It can perform a handover -+ * when exiting the unsafe region. Otherwise the waiter will -+ * need to perform an unsafe hostile takeover. -+ */ -+ if (cur->unsafe) -+ return true; -+ -+ /* Waiters always have higher priorities than owners. */ -+ WARN_ON_ONCE(cur->req_prio <= cur->prio); -+ -+ /* -+ * Having a safe point for take over and eventually a few -+ * duplicated characters or a full line is way better than a -+ * hostile takeover. Post processing can take care of the garbage. -+ * Release and hand over. -+ */ -+ nbcon_context_release(ctxt); -+ -+ /* -+ * It is not clear whether the waiter really took over ownership. The -+ * outermost callsite must make the final decision whether console -+ * ownership is needed for it to proceed. If yes, it must reacquire -+ * ownership (possibly hostile) before carefully proceeding. -+ * -+ * The calling context no longer owns the console so go back all the -+ * way instead of trying to implement reacquire heuristics in tons of -+ * places. -+ */ -+ return false; -+} -+ -+#define nbcon_context_enter_unsafe(c) __nbcon_context_update_unsafe(c, true) -+#define nbcon_context_exit_unsafe(c) __nbcon_context_update_unsafe(c, false) -+ -+/** -+ * __nbcon_context_update_unsafe - Update the unsafe bit in @con->nbcon_state -+ * @ctxt: The nbcon context from nbcon_context_try_acquire() -+ * @unsafe: The new value for the unsafe bit -+ * -+ * Return: True if the unsafe state was updated and this context still -+ * owns the console. Otherwise false if ownership was handed -+ * over or taken. -+ * -+ * This function allows console owners to modify the unsafe status of the -+ * console. -+ * -+ * 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. -+ * -+ * 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; -+ struct nbcon_state cur; -+ struct nbcon_state new; -+ -+ nbcon_state_read(con, &cur); -+ -+ do { -+ /* -+ * The unsafe bit must not be cleared if an -+ * unsafe hostile takeover has occurred. -+ */ -+ if (!unsafe && cur.unsafe_takeover) -+ goto out; -+ -+ if (!nbcon_context_can_proceed(ctxt, &cur)) -+ return false; -+ -+ new.atom = cur.atom; -+ new.unsafe = unsafe; -+ } while (!nbcon_state_try_cmpxchg(con, &cur, &new)); -+ -+ cur.atom = new.atom; -+out: -+ return nbcon_context_can_proceed(ctxt, &cur); -+} -+ -+/** - * nbcon_alloc - Allocate buffers needed by the nbcon console - * @con: Console to allocate buffers for - * |