From: Andrew Morton <andrewm@uow.edu.au>
To: Linus Torvalds <torvalds@transmeta.com>
Cc: lkml <linux-kernel@vger.kernel.org>
Subject: IGNORE Previous! [patch] Removal of oops->printk deadlocks
Date: Sat, 18 Nov 2000 14:53:27 +1100 [thread overview]
Message-ID: <3A15FD37.7F5D05CF@uow.edu.au> (raw)
[ Sorry - the last one was bogus test11-pre4 stuff ]
Linus,
this patch removes the final things which can cause oopses and other
sad events to deadlock without providing diagnostics.
I've changed it a little since Ingo provided comments - the
poke_blanked_console() changes have been simplified.
- If four places: oops, die(), NMI-oops and BUG() we call
bust_spinlocks(1) to set `oops_in_progress' to tell the printk and
console systems that they should not acquire any locks.
- After the message has gone out we call bust_spinlocks(0) to turn
off oops_in_progress and to do a 'printk(" \b");'. This allows
printk() to wake up klogd and allows the vgacon driver to turn the
screen back on.
- The NMI oopser has been enhanced so you can optionally get the NMI
oops traces for all the CPUs. You boot your kernel with the option:
nmi_watchdog=1,verbose
This is for those fun situations where your machine wedges after an
NMI oops.
- This is pretty specific to x86/vgacon, but everything is in place
for other architectures.
--- linux-2.4.0-test11-pre7/include/linux/kernel.h Sat Nov 18 13:55:32 2000
+++ linux-akpm/include/linux/kernel.h Sat Nov 18 14:44:08 2000
@@ -66,6 +66,7 @@
asmlinkage int printk(const char * fmt, ...)
__attribute__ ((format (printf, 1, 2)));
+extern int oops_in_progress;
#if DEBUG
#define pr_debug(fmt,arg...) \
--- linux-2.4.0-test11-pre7/include/asm-i386/page.h Sat Nov 4 16:22:49 2000
+++ linux-akpm/include/asm-i386/page.h Sat Nov 18 14:44:08 2000
@@ -88,8 +88,9 @@
* Tell the user there is some problem. Beep too, so we can
* see^H^H^Hhear bugs in early bootup as well!
*/
+extern void do_BUG(const char *file, int line);
#define BUG() do { \
- printk("kernel BUG at %s:%d!\n", __FILE__, __LINE__); \
+ do_BUG(__FILE__, __LINE__); \
__asm__ __volatile__(".byte 0x0f,0x0b"); \
} while (0)
--- linux-2.4.0-test11-pre7/kernel/printk.c Sat Nov 4 16:22:49 2000
+++ linux-akpm/kernel/printk.c Sat Nov 18 14:44:08 2000
@@ -51,6 +51,7 @@
static unsigned long logged_chars;
struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
static int preferred_console = -1;
+int oops_in_progress;
/*
* Setup a list of consoles. Called from init/main.c
@@ -260,6 +261,8 @@
static signed char msg_level = -1;
long flags;
+ if (oops_in_progress)
+ spin_lock_init(&console_lock);
spin_lock_irqsave(&console_lock, flags);
va_start(args, fmt);
i = vsprintf(buf + 3, fmt, args); /* hopefully i < sizeof(buf)-4 */
@@ -308,7 +311,8 @@
msg_level = -1;
}
spin_unlock_irqrestore(&console_lock, flags);
- wake_up_interruptible(&log_wait);
+ if (!oops_in_progress)
+ wake_up_interruptible(&log_wait);
return i;
}
--- linux-2.4.0-test11-pre7/arch/i386/mm/fault.c Sat Nov 18 13:55:28 2000
+++ linux-akpm/arch/i386/mm/fault.c Sat Nov 18 14:44:08 2000
@@ -24,6 +24,7 @@
#include <asm/hardirq.h>
extern void die(const char *,struct pt_regs *,long);
+extern int console_loglevel;
/*
* Ugly, ugly, but the goto's result in better assembly..
@@ -77,17 +78,40 @@
return 0;
}
-extern spinlock_t console_lock, timerlist_lock;
+#ifdef CONFIG_SMP
+extern unsigned volatile int global_irq_lock;
+#endif
/*
* Unlock any spinlocks which will prevent us from getting the
- * message out (timerlist_lock is aquired through the
- * console unblank code)
+ * message out and tell the printk/console paths that an emergency
+ * message is coming through
*/
-void bust_spinlocks(void)
+void bust_spinlocks(int yes)
{
- spin_lock_init(&console_lock);
- spin_lock_init(&timerlist_lock);
+ if (yes) {
+ oops_in_progress = 1;
+#ifdef CONFIG_SMP
+ global_irq_lock = 0; /* Many serial drivers do __global_cli() */
+#endif
+ } else {
+ int loglevel_save = console_loglevel;
+ oops_in_progress = 0;
+ /*
+ * OK, the message is on the console. Now we call printk()
+ * without oops_in_progress set so that printk will give klogd
+ * a poke. Hold onto your hats...
+ */
+ console_loglevel = 15; /* NMI oopser may have shut the console up */
+ printk(" \b");
+ console_loglevel = loglevel_save;
+ }
+}
+
+void do_BUG(const char *file, int line)
+{
+ bust_spinlocks(1);
+ printk("kernel BUG at %s:%d!\n", file, line);
}
asmlinkage void do_invalid_op(struct pt_regs *, unsigned long);
@@ -264,8 +288,7 @@
* terminate things with extreme prejudice.
*/
- bust_spinlocks();
-
+ bust_spinlocks(1);
if (address < PAGE_SIZE)
printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference");
else
@@ -283,6 +306,7 @@
printk(KERN_ALERT "*pte = %08lx\n", page);
}
die("Oops", regs, error_code);
+ bust_spinlocks(0);
do_exit(SIGKILL);
/*
--- linux-2.4.0-test11-pre7/arch/i386/kernel/traps.c Sat Nov 18 13:55:28 2000
+++ linux-akpm/arch/i386/kernel/traps.c Sat Nov 18 14:44:08 2000
@@ -63,7 +63,7 @@
struct desc_struct idt_table[256] __attribute__((__section__(".data.idt"))) = { {0, 0}, };
extern int console_loglevel;
-extern void bust_spinlocks(void);
+extern void bust_spinlocks(int yes);
static inline void console_silent(void)
{
@@ -209,9 +209,10 @@
{
console_verbose();
spin_lock_irq(&die_lock);
+ bust_spinlocks(1);
printk("%s: %04lx\n", str, err & 0xffff);
show_registers(regs);
-
+ bust_spinlocks(0);
spin_unlock_irq(&die_lock);
do_exit(SIGSEGV);
}
@@ -386,10 +387,14 @@
#if CONFIG_X86_IO_APIC
int nmi_watchdog = 1;
+static int nmi_watchdog_verbose;
static int __init setup_nmi_watchdog(char *str)
{
- get_option(&str, &nmi_watchdog);
+ if (get_option(&str, &nmi_watchdog) == 2) {
+ if (strcmp(str, "verbose") == 0)
+ nmi_watchdog_verbose = 1;
+ }
return 1;
}
@@ -414,7 +419,7 @@
* here too!]
*/
- static unsigned int last_irq_sums [NR_CPUS],
+ static unsigned int last_irq_sums [NR_CPUS],
alert_counter [NR_CPUS];
/*
@@ -437,12 +442,15 @@
* We are in trouble anyway, lets at least try
* to get a message out.
*/
- bust_spinlocks();
+ bust_spinlocks(1);
printk("NMI Watchdog detected LOCKUP on CPU%d, registers:\n", cpu);
show_registers(regs);
- printk("console shuts up ...\n");
- console_silent();
+ if (nmi_watchdog_verbose == 0) {
+ printk("Console shuts up. Run dmesg or boot with `nmi_watchdog=1,verbose' for more logs\n");
+ console_silent();
+ }
spin_unlock(&nmi_print_lock);
+ bust_spinlocks(0);
do_exit(SIGSEGV);
}
} else {
--- linux-2.4.0-test11-pre7/arch/i386/kernel/i386_ksyms.c Sat Nov 18 13:55:28 2000
+++ linux-akpm/arch/i386/kernel/i386_ksyms.c Sat Nov 18 14:44:08 2000
@@ -157,3 +157,5 @@
#ifdef CONFIG_X86_PAE
EXPORT_SYMBOL(empty_zero_page);
#endif
+
+EXPORT_SYMBOL(do_BUG);
--- linux-2.4.0-test11-pre7/drivers/char/console.c Sat Nov 18 13:55:28 2000
+++ linux-akpm/drivers/char/console.c Sat Nov 18 14:44:08 2000
@@ -2135,7 +2135,8 @@
}
}
set_cursor(currcons);
-
+ if (!oops_in_progress)
+ poke_blanked_console();
quit:
clear_bit(0, &printing);
}
--- linux-2.4.0-test11-pre7/Documentation/nmi_watchdog.txt Thu Aug 24 21:07:14 2000
+++ linux-akpm/Documentation/nmi_watchdog.txt Sat Nov 18 14:44:08 2000
@@ -24,8 +24,21 @@
cannot even accept NMI interrupts, or the crash has made the kernel
unable to print messages.
-NOTE: currently the NMI-oopser is enabled unconditionally on x86 SMP
-boxes.
+The NMI-oopser defaults to `1' (enabled) on x86 SMP boxes.
+
+The NMI-oopser only displays the first oops message on the console. This
+is to prevent vital information from scrolling off the scren if more
+errors occur. You can find additional information (such as NMI oops
+information from other CPUs) by looking in your system logs or with
+the `dmesg' command.
+
+If your system is crashing hard and preventing you from running `dmesg'
+you can tell the NMI oopser to display all NMI oops messages (not just
+the first one) by setting
+
+ nmi_watchdog=1,verbose
+
+on the kernel boot command line or in lilo.conf, as shown above.
[ feel free to send bug reports, suggestions and patches to
Ingo Molnar <mingo@redhat.com> or the Linux SMP mailing
-
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