diff options
Diffstat (limited to 'debian/patches-rt/0099-console-add-write_atomic-interface.patch')
| -rw-r--r-- | debian/patches-rt/0099-console-add-write_atomic-interface.patch | 163 |
1 files changed, 163 insertions, 0 deletions
diff --git a/debian/patches-rt/0099-console-add-write_atomic-interface.patch b/debian/patches-rt/0099-console-add-write_atomic-interface.patch new file mode 100644 index 000000000..86f553013 --- /dev/null +++ b/debian/patches-rt/0099-console-add-write_atomic-interface.patch @@ -0,0 +1,163 @@ +From a021f069828ba9181d19f5ee9a977cf305ddaf19 Mon Sep 17 00:00:00 2001 +From: John Ogness <john.ogness@linutronix.de> +Date: Mon, 30 Nov 2020 01:42:01 +0106 +Subject: [PATCH 099/323] console: add write_atomic interface +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.204-rt100.tar.xz + +Add a write_atomic() callback to the console. This is an optional +function for console drivers. The function must be atomic (including +NMI safe) for writing to the console. + +Console drivers must still implement the write() callback. The +write_atomic() callback will only be used in special situations, +such as when the kernel panics. + +Creating an NMI safe write_atomic() that must synchronize with +write() requires a careful implementation of the console driver. To +aid with the implementation, a set of console_atomic_*() functions +are provided: + + void console_atomic_lock(unsigned int *flags); + void console_atomic_unlock(unsigned int flags); + +These functions synchronize using a processor-reentrant spinlock +(called a cpulock). + +Signed-off-by: John Ogness <john.ogness@linutronix.de> +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + include/linux/console.h | 4 ++ + kernel/printk/printk.c | 100 ++++++++++++++++++++++++++++++++++++++++ + 2 files changed, 104 insertions(+) + +diff --git a/include/linux/console.h b/include/linux/console.h +index bc2a749e6f0d..613df76903f5 100644 +--- a/include/linux/console.h ++++ b/include/linux/console.h +@@ -141,6 +141,7 @@ static inline int con_debug_leave(void) + struct console { + char name[16]; + void (*write)(struct console *, const char *, unsigned); ++ void (*write_atomic)(struct console *co, const char *s, unsigned int count); + int (*read)(struct console *, char *, unsigned); + struct tty_driver *(*device)(struct console *, int *); + void (*unblank)(void); +@@ -232,4 +233,7 @@ extern void console_init(void); + void dummycon_register_output_notifier(struct notifier_block *nb); + void dummycon_unregister_output_notifier(struct notifier_block *nb); + ++extern void console_atomic_lock(unsigned int *flags); ++extern void console_atomic_unlock(unsigned int flags); ++ + #endif /* _LINUX_CONSOLE_H */ +diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c +index 57f3b8d7f35c..8768473712b2 100644 +--- a/kernel/printk/printk.c ++++ b/kernel/printk/printk.c +@@ -3551,3 +3551,103 @@ void kmsg_dump_rewind(struct kmsg_dumper_iter *iter) + EXPORT_SYMBOL_GPL(kmsg_dump_rewind); + + #endif ++ ++struct prb_cpulock { ++ atomic_t owner; ++ unsigned long __percpu *irqflags; ++}; ++ ++#define DECLARE_STATIC_PRINTKRB_CPULOCK(name) \ ++static DEFINE_PER_CPU(unsigned long, _##name##_percpu_irqflags); \ ++static struct prb_cpulock name = { \ ++ .owner = ATOMIC_INIT(-1), \ ++ .irqflags = &_##name##_percpu_irqflags, \ ++} ++ ++static bool __prb_trylock(struct prb_cpulock *cpu_lock, ++ unsigned int *cpu_store) ++{ ++ unsigned long *flags; ++ unsigned int cpu; ++ ++ cpu = get_cpu(); ++ ++ *cpu_store = atomic_read(&cpu_lock->owner); ++ /* memory barrier to ensure the current lock owner is visible */ ++ smp_rmb(); ++ if (*cpu_store == -1) { ++ flags = per_cpu_ptr(cpu_lock->irqflags, cpu); ++ local_irq_save(*flags); ++ if (atomic_try_cmpxchg_acquire(&cpu_lock->owner, ++ cpu_store, cpu)) { ++ return true; ++ } ++ local_irq_restore(*flags); ++ } else if (*cpu_store == cpu) { ++ return true; ++ } ++ ++ put_cpu(); ++ return false; ++} ++ ++/* ++ * prb_lock: Perform a processor-reentrant spin lock. ++ * @cpu_lock: A pointer to the lock object. ++ * @cpu_store: A "flags" pointer to store lock status information. ++ * ++ * If no processor has the lock, the calling processor takes the lock and ++ * becomes the owner. If the calling processor is already the owner of the ++ * lock, this function succeeds immediately. If lock is locked by another ++ * processor, this function spins until the calling processor becomes the ++ * owner. ++ * ++ * It is safe to call this function from any context and state. ++ */ ++static void prb_lock(struct prb_cpulock *cpu_lock, unsigned int *cpu_store) ++{ ++ for (;;) { ++ if (__prb_trylock(cpu_lock, cpu_store)) ++ break; ++ cpu_relax(); ++ } ++} ++ ++/* ++ * prb_unlock: Perform a processor-reentrant spin unlock. ++ * @cpu_lock: A pointer to the lock object. ++ * @cpu_store: A "flags" object storing lock status information. ++ * ++ * Release the lock. The calling processor must be the owner of the lock. ++ * ++ * It is safe to call this function from any context and state. ++ */ ++static void prb_unlock(struct prb_cpulock *cpu_lock, unsigned int cpu_store) ++{ ++ unsigned long *flags; ++ unsigned int cpu; ++ ++ cpu = atomic_read(&cpu_lock->owner); ++ atomic_set_release(&cpu_lock->owner, cpu_store); ++ ++ if (cpu_store == -1) { ++ flags = per_cpu_ptr(cpu_lock->irqflags, cpu); ++ local_irq_restore(*flags); ++ } ++ ++ put_cpu(); ++} ++ ++DECLARE_STATIC_PRINTKRB_CPULOCK(printk_cpulock); ++ ++void console_atomic_lock(unsigned int *flags) ++{ ++ prb_lock(&printk_cpulock, flags); ++} ++EXPORT_SYMBOL(console_atomic_lock); ++ ++void console_atomic_unlock(unsigned int flags) ++{ ++ prb_unlock(&printk_cpulock, flags); ++} ++EXPORT_SYMBOL(console_atomic_unlock); +-- +2.43.0 + |