diff options
Diffstat (limited to 'debian/patches-rt/0012-printk-nbcon-Use-driver-synchronization-while-regist.patch')
| -rw-r--r-- | debian/patches-rt/0012-printk-nbcon-Use-driver-synchronization-while-regist.patch | 68 |
1 files changed, 68 insertions, 0 deletions
diff --git a/debian/patches-rt/0012-printk-nbcon-Use-driver-synchronization-while-regist.patch b/debian/patches-rt/0012-printk-nbcon-Use-driver-synchronization-while-regist.patch new file mode 100644 index 0000000000..71afdf6e29 --- /dev/null +++ b/debian/patches-rt/0012-printk-nbcon-Use-driver-synchronization-while-regist.patch @@ -0,0 +1,68 @@ +From: John Ogness <john.ogness@linutronix.de> +Date: Fri, 15 Mar 2024 15:38:22 +0000 +Subject: [PATCH 12/48] printk: nbcon: Use driver synchronization while + registering +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.8/older/patches-6.8.2-rt11.tar.xz + +Depending on if an nbcon console is registered, a driver may +handle its internal locking differently. If a driver is holding +its internal lock while the nbcon console is registered, there +may be a risk that two different contexts access the hardware +simultaneously without synchronization. (For example, if the +printk subsystem invokes atomic printing while another driver +context acquired the internal lock without considering the +atomic console.) + +Use the driver synchronization while a registering nbcon console +transitions to being registered. This guarantees that if the +driver acquires its internal lock when the nbcon console was not +registered, it will remain unregistered until that context +releases the lock. + +Signed-off-by: John Ogness <john.ogness@linutronix.de> +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + kernel/printk/printk.c | 18 ++++++++++++++++++ + 1 file changed, 18 insertions(+) + +--- a/kernel/printk/printk.c ++++ b/kernel/printk/printk.c +@@ -3453,6 +3453,7 @@ void register_console(struct console *ne + struct console *con; + bool bootcon_registered = false; + bool realcon_registered = false; ++ unsigned long flags; + int err; + + console_list_lock(); +@@ -3545,6 +3546,19 @@ void register_console(struct console *ne + } + + /* ++ * If another context is actively using the hardware of this new ++ * console, it will not be aware of the nbcon synchronization. This ++ * is a risk that two contexts could access the hardware ++ * simultaneously if this new console is used for atomic printing ++ * and the other context is still using the hardware. ++ * ++ * Use the driver synchronization to ensure that the hardware is not ++ * in use while this new console transitions to being registered. ++ */ ++ if ((newcon->flags & CON_NBCON) && newcon->write_atomic) ++ newcon->device_lock(newcon, &flags); ++ ++ /* + * Put this console in the list - keep the + * preferred driver at the head of the list. + */ +@@ -3568,6 +3582,10 @@ void register_console(struct console *ne + * register_console() completes. + */ + ++ /* This new console is now registered. */ ++ if ((newcon->flags & CON_NBCON) && newcon->write_atomic) ++ newcon->device_unlock(newcon, flags); ++ + console_sysfs_notify(); + + /* |