diff options
Diffstat (limited to 'debian/patches-rt/0045-printk-Provide-threadprintk-boot-argument.patch')
| -rw-r--r-- | debian/patches-rt/0045-printk-Provide-threadprintk-boot-argument.patch | 96 |
1 files changed, 96 insertions, 0 deletions
diff --git a/debian/patches-rt/0045-printk-Provide-threadprintk-boot-argument.patch b/debian/patches-rt/0045-printk-Provide-threadprintk-boot-argument.patch new file mode 100644 index 0000000000..afb91f6f64 --- /dev/null +++ b/debian/patches-rt/0045-printk-Provide-threadprintk-boot-argument.patch @@ -0,0 +1,96 @@ +From: John Ogness <john.ogness@linutronix.de> +Date: Tue, 6 Feb 2024 14:19:34 +0000 +Subject: [PATCH 45/46] printk: Provide threadprintk boot argument +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.9/older/patches-6.9-rt5.tar.xz + +For PREEMPT_RT, legacy console printing is performed in a dedicated +kthread. However, this behavior can also be interesting for other +preemption models as it minimizes the duration of printk() calls by +deferring all printing. + +Provide a new boot argument "threadprintk" that will create the +dedicated kthread for legacy console printing for !PREEMPT_RT +systems. + +The implementation is the same as "threadirqs" boot argument. + +Users should be aware that if this option is enabled, the shutdown, +reboot, and panic messages probably will not be visible on the +legacy consoles. + +Non-legacy consoles (NBCON) already have their own dedicated kernel +threads for printing and reliable shutdown, reboot, and panic +printing. This option really only applies to legacy consoles. + +Users can view /proc/consoles to see if their console driver is +legacy or not. NBCON console drivers are shown with 'N'. + +Signed-off-by: John Ogness <john.ogness@linutronix.de> +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + Documentation/admin-guide/kernel-parameters.txt | 12 ++++++++++++ + kernel/printk/internal.h | 4 +++- + kernel/printk/printk.c | 11 +++++++++++ + 3 files changed, 26 insertions(+), 1 deletion(-) + +--- a/Documentation/admin-guide/kernel-parameters.txt ++++ b/Documentation/admin-guide/kernel-parameters.txt +@@ -6552,6 +6552,18 @@ + Force threading of all interrupt handlers except those + marked explicitly IRQF_NO_THREAD. + ++ threadprintk [KNL] ++ Force threaded printing of all legacy consoles. Be ++ aware that with this option, the shutdown, reboot, and ++ panic messages may not be printed on the legacy ++ consoles. Also, earlycon/earlyprintk printing will be ++ delayed until a regular console or the kthread is ++ available. ++ ++ Users can view /proc/consoles to see if their console ++ driver is legacy or not. Non-legacy (NBCON) console ++ drivers are already threaded and are shown with 'N'. ++ + topology= [S390,EARLY] + Format: {off | on} + Specify if the kernel should make use of the cpu +--- a/kernel/printk/internal.h ++++ b/kernel/printk/internal.h +@@ -3,6 +3,7 @@ + * internal.h - printk internal definitions + */ + #include <linux/console.h> ++#include <linux/jump_label.h> + #include <linux/percpu.h> + #include <linux/types.h> + +@@ -24,7 +25,8 @@ int devkmsg_sysctl_set_loglvl(struct ctl + #ifdef CONFIG_PREEMPT_RT + # define force_printkthreads() (true) + #else +-# define force_printkthreads() (false) ++DECLARE_STATIC_KEY_FALSE(force_printkthreads_key); ++# define force_printkthreads() (static_branch_unlikely(&force_printkthreads_key)) + #endif + + #ifdef CONFIG_PRINTK +--- a/kernel/printk/printk.c ++++ b/kernel/printk/printk.c +@@ -195,6 +195,17 @@ static int __init control_devkmsg(char * + } + __setup("printk.devkmsg=", control_devkmsg); + ++#if !defined(CONFIG_PREEMPT_RT) ++DEFINE_STATIC_KEY_FALSE(force_printkthreads_key); ++ ++static int __init setup_forced_printkthreads(char *arg) ++{ ++ static_branch_enable(&force_printkthreads_key); ++ return 0; ++} ++early_param("threadprintk", setup_forced_printkthreads); ++#endif ++ + char devkmsg_log_str[DEVKMSG_STR_MAX_SIZE] = "ratelimit"; + #if defined(CONFIG_PRINTK) && defined(CONFIG_SYSCTL) + int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write, |