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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-18 18:47:59 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-18 18:47:59 +0000
commit8c87665b42c616a0d83837405ed44e90d1cacaee (patch)
tree7aa741e9343d0b73b2f72ea1b78ef8785653288b /debian/patches-rt/0012-printk-Disable-passing-console-lock-owner-completely.patch
parentMerging upstream version 6.7.12. (diff)
downloadlinux-8c87665b42c616a0d83837405ed44e90d1cacaee.tar.xz
linux-8c87665b42c616a0d83837405ed44e90d1cacaee.zip
Adding debian version 6.7.12-1.debian/6.7.12-1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'debian/patches-rt/0012-printk-Disable-passing-console-lock-owner-completely.patch')
-rw-r--r--debian/patches-rt/0012-printk-Disable-passing-console-lock-owner-completely.patch107
1 files changed, 0 insertions, 107 deletions
diff --git a/debian/patches-rt/0012-printk-Disable-passing-console-lock-owner-completely.patch b/debian/patches-rt/0012-printk-Disable-passing-console-lock-owner-completely.patch
deleted file mode 100644
index adc25ac39d..0000000000
--- a/debian/patches-rt/0012-printk-Disable-passing-console-lock-owner-completely.patch
+++ /dev/null
@@ -1,107 +0,0 @@
-From: Petr Mladek <pmladek@suse.com>
-Date: Fri, 13 Oct 2023 14:12:05 +0000
-Subject: [PATCH 12/50] printk: Disable passing console lock owner completely
- during panic()
-Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.7/older/patches-6.7-rt6.tar.xz
-
-The commit d51507098ff91 ("printk: disable optimistic spin
-during panic") added checks to avoid becoming a console waiter
-if a panic is in progress.
-
-However, the transition to panic can occur while there is
-already a waiter. The current owner should not pass the lock to
-the waiter because it might get stopped or blocked anytime.
-
-Also the panic context might pass the console lock owner to an
-already stopped waiter by mistake. It might happen when
-console_flush_on_panic() ignores the current lock owner, for
-example:
-
-CPU0 CPU1
----- ----
-console_lock_spinning_enable()
- console_trylock_spinning()
- [CPU1 now console waiter]
-NMI: panic()
- panic_other_cpus_shutdown()
- [stopped as console waiter]
- console_flush_on_panic()
- console_lock_spinning_enable()
- [print 1 record]
- console_lock_spinning_disable_and_check()
- [handover to stopped CPU1]
-
-This results in panic() not flushing the panic messages.
-
-Fix these problems by disabling all spinning operations
-completely during panic().
-
-Another advantage is that it prevents possible deadlocks caused
-by "console_owner_lock". The panic() context does not need to
-take it any longer. The lockless checks are safe because the
-functions become NOPs when they see the panic in progress. All
-operations manipulating the state are still synchronized by the
-lock even when non-panic CPUs would notice the panic
-synchronously.
-
-The current owner might stay spinning. But non-panic() CPUs
-would get stopped anyway and the panic context will never start
-spinning.
-
-Fixes: dbdda842fe96 ("printk: Add console owner and waiter logic to load balance console writes")
-Signed-off-by: Petr Mladek <pmladek@suse.com>
-Signed-off-by: John Ogness <john.ogness@linutronix.de>
-Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
----
- kernel/printk/printk.c | 29 +++++++++++++++++++++++++++++
- 1 file changed, 29 insertions(+)
-
---- a/kernel/printk/printk.c
-+++ b/kernel/printk/printk.c
-@@ -1869,10 +1869,23 @@ static bool console_waiter;
- */
- static void console_lock_spinning_enable(void)
- {
-+ /*
-+ * Do not use spinning in panic(). The panic CPU wants to keep the lock.
-+ * Non-panic CPUs abandon the flush anyway.
-+ *
-+ * Just keep the lockdep annotation. The panic-CPU should avoid
-+ * taking console_owner_lock because it might cause a deadlock.
-+ * This looks like the easiest way how to prevent false lockdep
-+ * reports without handling races a lockless way.
-+ */
-+ if (panic_in_progress())
-+ goto lockdep;
-+
- raw_spin_lock(&console_owner_lock);
- console_owner = current;
- raw_spin_unlock(&console_owner_lock);
-
-+lockdep:
- /* The waiter may spin on us after setting console_owner */
- spin_acquire(&console_owner_dep_map, 0, 0, _THIS_IP_);
- }
-@@ -1897,6 +1910,22 @@ static int console_lock_spinning_disable
- {
- int waiter;
-
-+ /*
-+ * Ignore spinning waiters during panic() because they might get stopped
-+ * or blocked at any time,
-+ *
-+ * It is safe because nobody is allowed to start spinning during panic
-+ * in the first place. If there has been a waiter then non panic CPUs
-+ * might stay spinning. They would get stopped anyway. The panic context
-+ * will never start spinning and an interrupted spin on panic CPU will
-+ * never continue.
-+ */
-+ if (panic_in_progress()) {
-+ /* Keep lockdep happy. */
-+ spin_release(&console_owner_dep_map, _THIS_IP_);
-+ return 0;
-+ }
-+
- raw_spin_lock(&console_owner_lock);
- waiter = READ_ONCE(console_waiter);
- console_owner = NULL;