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SubjectRe: [PATCH v2] panic: add an option to replay all the printk message in buffer
On (04/17/19 18:46), Sergey Senozhatsky wrote:
>
> Does not look too complex/ugly.

Looks simpler than adding one more global state to the
console_unlock() printing loop.

// Not tested at all //

---

diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 1fd45a8650e1..0fb785ed5ec6 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -179,7 +179,7 @@ extern void panic_flush_kmsg_end(void)
kmsg_dump(KMSG_DUMP_PANIC);
bust_spinlocks(0);
debug_locks_off();
- console_flush_on_panic();
+ console_flush_on_panic(CONSOLE_FLUSH_PENDING);
}

static unsigned long oops_begin(struct pt_regs *regs)
diff --git a/include/linux/console.h b/include/linux/console.h
index ec9bdb3d7bab..9e306eb4398a 100644
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -175,7 +175,13 @@ extern int console_trylock(void);
extern void console_unlock(void);
extern void console_conditional_schedule(void);
extern void console_unblank(void);
-extern void console_flush_on_panic(void);
+
+enum console_flush_mode {
+ CONSOLE_FLUSH_PENDING,
+ CONSOLE_FLUSH_ALL,
+};
+
+extern void console_flush_on_panic(enum console_flush_mode flush_mode);
extern struct tty_driver *console_device(int *);
extern void console_stop(struct console *);
extern void console_start(struct console *);
diff --git a/kernel/panic.c b/kernel/panic.c
index cd73af35ec66..50eacfc9bc7e 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -51,6 +51,7 @@ EXPORT_SYMBOL_GPL(panic_timeout);
#define PANIC_PRINT_TIMER_INFO 0x00000004
#define PANIC_PRINT_LOCK_INFO 0x00000008
#define PANIC_PRINT_FTRACE_INFO 0x00000010
+#define PANIC_PRINT_ALL_PRINTK_MSG 0x00000020
unsigned long panic_print;

ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
@@ -148,6 +149,9 @@ static void panic_print_sys_info(void)

if (panic_print & PANIC_PRINT_FTRACE_INFO)
ftrace_dump(DUMP_ALL);
+
+ if (panic_print & PANIC_PRINT_ALL_PRINTK_MSG)
+ console_flush_on_panic(CONSOLE_FLUSH_ALL);
}

/**
@@ -277,7 +281,7 @@ void panic(const char *fmt, ...)
* panic() is not being callled from OOPS.
*/
debug_locks_off();
- console_flush_on_panic();
+ console_flush_on_panic(CONSOLE_FLUSH_PENDING);

panic_print_sys_info();

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 17102fd4c136..da60a185dbbb 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2538,7 +2538,7 @@ void console_unblank(void)
*
* Immediately output all pending messages no matter what.
*/
-void console_flush_on_panic(void)
+void console_flush_on_panic(enum console_flush_mode flush_mode)
{
/*
* If someone else is holding the console lock, trylock will fail
@@ -2549,6 +2549,14 @@ void console_flush_on_panic(void)
*/
console_trylock();
console_may_schedule = 0;
+ if (flush_mode == CONSOLE_FLUSH_ALL) {
+ /*
+ * Can be done under logbuf lock, but it's unlikely that
+ * we will have any race conditions here.
+ */
+ console_seq = log_first_seq;
+ console_idx = log_first_idx;
+ }
console_unlock();
}

---
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