summaryrefslogtreecommitdiffstats
path: root/debian/patches-rt/0079-printk-nbcon-Add-ownership-state-functions.patch
diff options
context:
space:
mode:
Diffstat (limited to 'debian/patches-rt/0079-printk-nbcon-Add-ownership-state-functions.patch')
-rw-r--r--debian/patches-rt/0079-printk-nbcon-Add-ownership-state-functions.patch179
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
- *