On 05.06.2011 15:39, Ingo Molnar wrote:
* Arne Jansen<lists@xxxxxxxxxxxxxx> wrote:Warning: it's entirely untested.How is the output supposed to come through? shouldn't printk revert to early_printk instead of just returning?oh, right you are. Does the patch below work? It does early-printk within printk().
Too late, I already built my on early_vprintk ;) Here we go: http://eischnee.de/lockup.txt Now it's your turn :) -Arne
Thanks,
Ingo
diff --git a/arch/x86/kernel/early_printk.c b/arch/x86/kernel/early_printk.c
index cd28a35..211d8c2 100644
--- a/arch/x86/kernel/early_printk.c
+++ b/arch/x86/kernel/early_printk.c
@@ -170,8 +170,8 @@ static struct console early_serial_console = {
};
/* Direct interface for emergencies */
-static struct console *early_console =&early_vga_console;
-static int __initdata early_console_initialized;
+struct console *early_console =&early_vga_console;
+int early_console_initialized;
asmlinkage void early_printk(const char *fmt, ...)
{
diff --git a/include/linux/printk.h b/include/linux/printk.h
index 0101d55..414dc34 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -88,6 +88,9 @@ int no_printk(const char *fmt, ...)
return 0;
}
+extern struct console *early_console;
+extern int early_console_initialized;
+
extern asmlinkage __attribute__ ((format (printf, 1, 2)))
void early_printk(const char *fmt, ...);
@@ -114,6 +117,8 @@ extern int printk_delay_msec;
extern int dmesg_restrict;
extern int kptr_restrict;
+extern void printk_kill(void);
+
void log_buf_kexec_setup(void);
void __init setup_log_buf(int early);
#else
diff --git a/kernel/printk.c b/kernel/printk.c
index 3518539..50684e3 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -519,6 +519,19 @@ static void __call_console_drivers(unsigned start, unsigned end)
}
}
+/*
+ * This is independent of any log levels - a global
+ * kill switch that turns off all of printk.
+ *
+ * Used by the NMI watchdog if early-printk is enabled.
+ */
+static int __read_mostly printk_killswitch;
+
+void printk_kill(void)
+{
+ printk_killswitch = 1;
+}
+
static int __read_mostly ignore_loglevel;
static int __init ignore_loglevel_setup(char *str)
@@ -833,6 +846,16 @@ asmlinkage int vprintk(const char *fmt, va_list args)
size_t plen;
char special;
+ /* Return early if a debugging subsystem has killed printk output: */
+ if (unlikely(printk_killswitch)) {
+ char buf[512];
+
+ printed_len = vscnprintf(buf, sizeof(buf), fmt, args);
+ early_console->write(early_console, buf, printed_len);
+
+ return printed_len;
+ }
+
boot_delay_msec();
printk_delay();
@@ -1533,6 +1556,7 @@ void register_console(struct console *newcon)
for_each_console(bcon)
if (bcon->flags& CON_BOOT)
unregister_console(bcon);
+ early_console_initialized = 0;
} else {
printk(KERN_INFO "%sconsole [%s%d] enabled\n",
(newcon->flags& CON_BOOT) ? "boot" : "" ,
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 3d0c56a..6e9b109 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -234,6 +234,13 @@ static void watchdog_overflow_callback(struct perf_event *event, int nmi,
if (__this_cpu_read(hard_watchdog_warn) == true)
return;
+ /*
+ * If early-printk is enabled then make sure we do not
+ * lock up in printk() and kill console logging:
+ */
+ if (early_console_initialized)
+ printk_kill();
+
if (hardlockup_panic)
panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
else
--
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