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-rw-r--r--debian/patches-rt/0106-printk-remove-deferred-printing.patch432
1 files changed, 432 insertions, 0 deletions
diff --git a/debian/patches-rt/0106-printk-remove-deferred-printing.patch b/debian/patches-rt/0106-printk-remove-deferred-printing.patch
new file mode 100644
index 000000000..b65397f57
--- /dev/null
+++ b/debian/patches-rt/0106-printk-remove-deferred-printing.patch
@@ -0,0 +1,432 @@
+From f1e8f72e9d5c1df1ddaac09999645f7255219d77 Mon Sep 17 00:00:00 2001
+From: John Ogness <john.ogness@linutronix.de>
+Date: Mon, 30 Nov 2020 01:42:08 +0106
+Subject: [PATCH 106/323] printk: remove deferred printing
+Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.204-rt100.tar.xz
+
+Since printing occurs either atomically or from the printing
+kthread, there is no need for any deferring or tracking possible
+recursion paths. Remove all printk context tracking.
+
+Signed-off-by: John Ogness <john.ogness@linutronix.de>
+Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+---
+ arch/arm/kernel/smp.c | 2 -
+ arch/powerpc/kexec/crash.c | 3 --
+ include/linux/hardirq.h | 2 -
+ include/linux/printk.h | 12 -----
+ kernel/printk/Makefile | 1 -
+ kernel/printk/internal.h | 70 -----------------------------
+ kernel/printk/printk.c | 58 ++++++++++--------------
+ kernel/printk/printk_safe.c | 88 -------------------------------------
+ kernel/trace/trace.c | 2 -
+ 9 files changed, 22 insertions(+), 216 deletions(-)
+ delete mode 100644 kernel/printk/internal.h
+ delete mode 100644 kernel/printk/printk_safe.c
+
+diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
+index 8aa7fa949c23..3693706ba0a1 100644
+--- a/arch/arm/kernel/smp.c
++++ b/arch/arm/kernel/smp.c
+@@ -671,9 +671,7 @@ static void do_handle_IPI(int ipinr)
+ break;
+
+ case IPI_CPU_BACKTRACE:
+- printk_nmi_enter();
+ nmi_cpu_backtrace(get_irq_regs());
+- printk_nmi_exit();
+ break;
+
+ default:
+diff --git a/arch/powerpc/kexec/crash.c b/arch/powerpc/kexec/crash.c
+index c9a889880214..d488311efab1 100644
+--- a/arch/powerpc/kexec/crash.c
++++ b/arch/powerpc/kexec/crash.c
+@@ -311,9 +311,6 @@ void default_machine_crash_shutdown(struct pt_regs *regs)
+ unsigned int i;
+ int (*old_handler)(struct pt_regs *regs);
+
+- /* Avoid hardlocking with irresponsive CPU holding logbuf_lock */
+- printk_nmi_enter();
+-
+ /*
+ * This function is only called after the system
+ * has panicked or is otherwise in a critical state.
+diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
+index 754f67ac4326..c35b71f8644a 100644
+--- a/include/linux/hardirq.h
++++ b/include/linux/hardirq.h
+@@ -115,7 +115,6 @@ extern void rcu_nmi_exit(void);
+ do { \
+ lockdep_off(); \
+ arch_nmi_enter(); \
+- printk_nmi_enter(); \
+ BUG_ON(in_nmi() == NMI_MASK); \
+ __preempt_count_add(NMI_OFFSET + HARDIRQ_OFFSET); \
+ } while (0)
+@@ -134,7 +133,6 @@ extern void rcu_nmi_exit(void);
+ do { \
+ BUG_ON(!in_nmi()); \
+ __preempt_count_sub(NMI_OFFSET + HARDIRQ_OFFSET); \
+- printk_nmi_exit(); \
+ arch_nmi_exit(); \
+ lockdep_on(); \
+ } while (0)
+diff --git a/include/linux/printk.h b/include/linux/printk.h
+index 3738374e2b3b..410435ac15ea 100644
+--- a/include/linux/printk.h
++++ b/include/linux/printk.h
+@@ -155,18 +155,6 @@ static inline __printf(1, 2) __cold
+ void early_printk(const char *s, ...) { }
+ #endif
+
+-#ifdef CONFIG_PRINTK_NMI
+-extern void printk_nmi_enter(void);
+-extern void printk_nmi_exit(void);
+-extern void printk_nmi_direct_enter(void);
+-extern void printk_nmi_direct_exit(void);
+-#else
+-static inline void printk_nmi_enter(void) { }
+-static inline void printk_nmi_exit(void) { }
+-static inline void printk_nmi_direct_enter(void) { }
+-static inline void printk_nmi_direct_exit(void) { }
+-#endif /* PRINTK_NMI */
+-
+ struct dev_printk_info;
+
+ #ifdef CONFIG_PRINTK
+diff --git a/kernel/printk/Makefile b/kernel/printk/Makefile
+index eee3dc9b60a9..59cb24e25f00 100644
+--- a/kernel/printk/Makefile
++++ b/kernel/printk/Makefile
+@@ -1,5 +1,4 @@
+ # SPDX-License-Identifier: GPL-2.0-only
+ obj-y = printk.o
+-obj-$(CONFIG_PRINTK) += printk_safe.o
+ obj-$(CONFIG_A11Y_BRAILLE_CONSOLE) += braille.o
+ obj-$(CONFIG_PRINTK) += printk_ringbuffer.o
+diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h
+deleted file mode 100644
+index e108b2ece8c7..000000000000
+--- a/kernel/printk/internal.h
++++ /dev/null
+@@ -1,70 +0,0 @@
+-/* SPDX-License-Identifier: GPL-2.0-or-later */
+-/*
+- * internal.h - printk internal definitions
+- */
+-#include <linux/percpu.h>
+-
+-#ifdef CONFIG_PRINTK
+-
+-#define PRINTK_SAFE_CONTEXT_MASK 0x007ffffff
+-#define PRINTK_NMI_DIRECT_CONTEXT_MASK 0x008000000
+-#define PRINTK_NMI_CONTEXT_MASK 0xff0000000
+-
+-#define PRINTK_NMI_CONTEXT_OFFSET 0x010000000
+-
+-__printf(4, 0)
+-int vprintk_store(int facility, int level,
+- const struct dev_printk_info *dev_info,
+- const char *fmt, va_list args);
+-
+-__printf(1, 0) int vprintk_default(const char *fmt, va_list args);
+-__printf(1, 0) int vprintk_deferred(const char *fmt, va_list args);
+-__printf(1, 0) int vprintk_func(const char *fmt, va_list args);
+-void __printk_safe_enter(void);
+-void __printk_safe_exit(void);
+-
+-bool printk_percpu_data_ready(void);
+-
+-#define printk_safe_enter_irqsave(flags) \
+- do { \
+- local_irq_save(flags); \
+- __printk_safe_enter(); \
+- } while (0)
+-
+-#define printk_safe_exit_irqrestore(flags) \
+- do { \
+- __printk_safe_exit(); \
+- local_irq_restore(flags); \
+- } while (0)
+-
+-#define printk_safe_enter_irq() \
+- do { \
+- local_irq_disable(); \
+- __printk_safe_enter(); \
+- } while (0)
+-
+-#define printk_safe_exit_irq() \
+- do { \
+- __printk_safe_exit(); \
+- local_irq_enable(); \
+- } while (0)
+-
+-void defer_console_output(void);
+-
+-#else
+-
+-__printf(1, 0) int vprintk_func(const char *fmt, va_list args) { return 0; }
+-
+-/*
+- * In !PRINTK builds we still export console_sem
+- * semaphore and some of console functions (console_unlock()/etc.), so
+- * printk-safe must preserve the existing local IRQ guarantees.
+- */
+-#define printk_safe_enter_irqsave(flags) local_irq_save(flags)
+-#define printk_safe_exit_irqrestore(flags) local_irq_restore(flags)
+-
+-#define printk_safe_enter_irq() local_irq_disable()
+-#define printk_safe_exit_irq() local_irq_enable()
+-
+-static inline bool printk_percpu_data_ready(void) { return false; }
+-#endif /* CONFIG_PRINTK */
+diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
+index 232ce58e94c2..2b110b9ae34a 100644
+--- a/kernel/printk/printk.c
++++ b/kernel/printk/printk.c
+@@ -45,6 +45,7 @@
+ #include <linux/ctype.h>
+ #include <linux/uio.h>
+ #include <linux/kthread.h>
++#include <linux/kdb.h>
+ #include <linux/clocksource.h>
+ #include <linux/sched/clock.h>
+ #include <linux/sched/debug.h>
+@@ -60,7 +61,6 @@
+ #include "printk_ringbuffer.h"
+ #include "console_cmdline.h"
+ #include "braille.h"
+-#include "internal.h"
+
+ int console_printk[4] = {
+ CONSOLE_LOGLEVEL_DEFAULT, /* console_loglevel */
+@@ -229,19 +229,7 @@ static int nr_ext_console_drivers;
+
+ static int __down_trylock_console_sem(unsigned long ip)
+ {
+- int lock_failed;
+- unsigned long flags;
+-
+- /*
+- * Here and in __up_console_sem() we need to be in safe mode,
+- * because spindump/WARN/etc from under console ->lock will
+- * deadlock in printk()->down_trylock_console_sem() otherwise.
+- */
+- printk_safe_enter_irqsave(flags);
+- lock_failed = down_trylock(&console_sem);
+- printk_safe_exit_irqrestore(flags);
+-
+- if (lock_failed)
++ if (down_trylock(&console_sem))
+ return 1;
+ mutex_acquire(&console_lock_dep_map, 0, 1, ip);
+ return 0;
+@@ -250,13 +238,9 @@ static int __down_trylock_console_sem(unsigned long ip)
+
+ static void __up_console_sem(unsigned long ip)
+ {
+- unsigned long flags;
+-
+ mutex_release(&console_lock_dep_map, ip);
+
+- printk_safe_enter_irqsave(flags);
+ up(&console_sem);
+- printk_safe_exit_irqrestore(flags);
+ }
+ #define up_console_sem() __up_console_sem(_RET_IP_)
+
+@@ -428,7 +412,7 @@ static struct printk_ringbuffer *prb = &printk_rb_static;
+ */
+ static bool __printk_percpu_data_ready __read_mostly;
+
+-bool printk_percpu_data_ready(void)
++static bool printk_percpu_data_ready(void)
+ {
+ return __printk_percpu_data_ready;
+ }
+@@ -1063,7 +1047,6 @@ void __init setup_log_buf(int early)
+ struct printk_record r;
+ size_t new_descs_size;
+ size_t new_infos_size;
+- unsigned long flags;
+ char *new_log_buf;
+ unsigned int free;
+ u64 seq;
+@@ -1961,9 +1944,9 @@ static u16 printk_sprint(char *text, u16 size, int facility, enum log_flags *lfl
+ }
+
+ __printf(4, 0)
+-int vprintk_store(int facility, int level,
+- const struct dev_printk_info *dev_info,
+- const char *fmt, va_list args)
++static int vprintk_store(int facility, int level,
++ const struct dev_printk_info *dev_info,
++ const char *fmt, va_list args)
+ {
+ const u32 caller_id = printk_caller_id();
+ struct prb_reserved_entry e;
+@@ -2109,11 +2092,22 @@ asmlinkage int vprintk_emit(int facility, int level,
+ }
+ EXPORT_SYMBOL(vprintk_emit);
+
+-int vprintk_default(const char *fmt, va_list args)
++__printf(1, 0)
++static int vprintk_default(const char *fmt, va_list args)
+ {
+ return vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, fmt, args);
+ }
+-EXPORT_SYMBOL_GPL(vprintk_default);
++
++__printf(1, 0)
++static int vprintk_func(const char *fmt, va_list args)
++{
++#ifdef CONFIG_KGDB_KDB
++ /* Allow to pass printk() to kdb but avoid a recursion. */
++ if (unlikely(kdb_trap_printk && kdb_printf_cpu < 0))
++ return vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
++#endif
++ return vprintk_default(fmt, args);
++}
+
+ asmlinkage int vprintk(const char *fmt, va_list args)
+ {
+@@ -3078,18 +3072,10 @@ void wake_up_klogd(void)
+ preempt_enable();
+ }
+
+-void defer_console_output(void)
+-{
+-}
+-
+-int vprintk_deferred(const char *fmt, va_list args)
++__printf(1, 0)
++static int vprintk_deferred(const char *fmt, va_list args)
+ {
+- int r;
+-
+- r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, fmt, args);
+- defer_console_output();
+-
+- return r;
++ return vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, fmt, args);
+ }
+
+ int printk_deferred(const char *fmt, ...)
+diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c
+deleted file mode 100644
+index c23b127a6545..000000000000
+--- a/kernel/printk/printk_safe.c
++++ /dev/null
+@@ -1,88 +0,0 @@
+-// SPDX-License-Identifier: GPL-2.0-or-later
+-/*
+- * printk_safe.c - Safe printk for printk-deadlock-prone contexts
+- */
+-
+-#include <linux/preempt.h>
+-#include <linux/spinlock.h>
+-#include <linux/debug_locks.h>
+-#include <linux/kdb.h>
+-#include <linux/smp.h>
+-#include <linux/cpumask.h>
+-#include <linux/irq_work.h>
+-#include <linux/printk.h>
+-#include <linux/kprobes.h>
+-
+-#include "internal.h"
+-
+-static DEFINE_PER_CPU(int, printk_context);
+-
+-#ifdef CONFIG_PRINTK_NMI
+-void noinstr printk_nmi_enter(void)
+-{
+- this_cpu_add(printk_context, PRINTK_NMI_CONTEXT_OFFSET);
+-}
+-
+-void noinstr printk_nmi_exit(void)
+-{
+- this_cpu_sub(printk_context, PRINTK_NMI_CONTEXT_OFFSET);
+-}
+-
+-/*
+- * Marks a code that might produce many messages in NMI context
+- * and the risk of losing them is more critical than eventual
+- * reordering.
+- */
+-void printk_nmi_direct_enter(void)
+-{
+- if (this_cpu_read(printk_context) & PRINTK_NMI_CONTEXT_MASK)
+- this_cpu_or(printk_context, PRINTK_NMI_DIRECT_CONTEXT_MASK);
+-}
+-
+-void printk_nmi_direct_exit(void)
+-{
+- this_cpu_and(printk_context, ~PRINTK_NMI_DIRECT_CONTEXT_MASK);
+-}
+-
+-#endif /* CONFIG_PRINTK_NMI */
+-
+-/* Can be preempted by NMI. */
+-void __printk_safe_enter(void)
+-{
+- this_cpu_inc(printk_context);
+-}
+-
+-/* Can be preempted by NMI. */
+-void __printk_safe_exit(void)
+-{
+- this_cpu_dec(printk_context);
+-}
+-
+-__printf(1, 0) int vprintk_func(const char *fmt, va_list args)
+-{
+-#ifdef CONFIG_KGDB_KDB
+- /* Allow to pass printk() to kdb but avoid a recursion. */
+- if (unlikely(kdb_trap_printk && kdb_printf_cpu < 0))
+- return vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
+-#endif
+-
+- /*
+- * Use the main logbuf even in NMI. But avoid calling console
+- * drivers that might have their own locks.
+- */
+- if (this_cpu_read(printk_context) &
+- (PRINTK_NMI_DIRECT_CONTEXT_MASK |
+- PRINTK_NMI_CONTEXT_MASK |
+- PRINTK_SAFE_CONTEXT_MASK)) {
+- int len;
+-
+- printk_safe_enter_irqsave(flags);
+- len = vprintk_store(0, LOGLEVEL_DEFAULT, NULL, fmt, args);
+- printk_safe_exit_irqrestore(flags);
+- defer_console_output();
+- return len;
+- }
+-
+- /* No obstacles. */
+- return vprintk_default(fmt, args);
+-}
+diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
+index 70ab6b46ef8f..5d6730589823 100644
+--- a/kernel/trace/trace.c
++++ b/kernel/trace/trace.c
+@@ -9517,7 +9517,6 @@ void ftrace_dump(enum ftrace_dump_mode oops_dump_mode)
+ tracing_off();
+
+ local_irq_save(flags);
+- printk_nmi_direct_enter();
+
+ /* Simulate the iterator */
+ trace_init_global_iter(&iter);
+@@ -9594,7 +9593,6 @@ void ftrace_dump(enum ftrace_dump_mode oops_dump_mode)
+ atomic_dec(&per_cpu_ptr(iter.array_buffer->data, cpu)->disabled);
+ }
+ atomic_dec(&dump_running);
+- printk_nmi_direct_exit();
+ local_irq_restore(flags);
+ }
+ EXPORT_SYMBOL_GPL(ftrace_dump);
+--
+2.43.0
+