[PATCH] x86 NMI: better support for debuggers

This patch adds a notify to the die_nmi notify that the system is about to
be taken down.  If the notify is handled with a NOTIFY_STOP return, the
system is given a new lease on life.

We also change the nmi watchdog to carry on if die_nmi returns.

This give debug code a chance to a) catch watchdog timeouts and b) possibly
allow the system to continue, realizing that the time out may be due to
debugger activities such as single stepping which is usually done with
"other" cpus held.

Signed-off-by: George Anzinger<george@mvista.com>
Cc: Keith Owens <kaos@ocs.com.au>
Signed-off-by: George Anzinger <george@mvista.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/arch/i386/kernel/nmi.c b/arch/i386/kernel/nmi.c
index 8c242bb1ef4571685cebeb2c11c0160a92bc9695..8bbdbda07a2d6c0dd54d68ec06ea968b52d064fb 100644 (file)
--- a/arch/i386/kernel/nmi.c
+++ b/arch/i386/kernel/nmi.c
@@ -501,8 +501,11 @@ void nmi_watchdog_tick (struct pt_regs * regs)
                 */
                alert_counter[cpu]++;
                if (alert_counter[cpu] == 5*nmi_hz)
+                       /*
+                        * die_nmi will return ONLY if NOTIFY_STOP happens..
+                        */
                        die_nmi(regs, "NMI Watchdog detected LOCKUP");
-       } else {
+
                last_irq_sums[cpu] = sum;
                alert_counter[cpu] = 0;
        }

diff --git a/arch/i386/kernel/traps.c b/arch/i386/kernel/traps.c
index b2b4bb890bb74bea8b2ba9ae238c843477da7129..54629bb5893ae1c9ab6765ea6b84a23c1fae3761 100644 (file)
--- a/arch/i386/kernel/traps.c
+++ b/arch/i386/kernel/traps.c
@@ -565,6 +565,10 @@ static DEFINE_SPINLOCK(nmi_print_lock);
 
 void die_nmi (struct pt_regs *regs, const char *msg)
 {
+       if (notify_die(DIE_NMIWATCHDOG, msg, regs, 0, 0, SIGINT) ==
+           NOTIFY_STOP)
+               return;
+
        spin_lock(&nmi_print_lock);
        /*
        * We are in trouble anyway, lets at least try

diff --git a/include/asm-i386/kdebug.h b/include/asm-i386/kdebug.h
index b3f8d5f59d5d8fc02cc1c5f88bce01921c641496..316138e89910743f3a1b265ca4f04741bdffdc98 100644 (file)
--- a/include/asm-i386/kdebug.h
+++ b/include/asm-i386/kdebug.h
@@ -41,9 +41,16 @@ enum die_val {
        DIE_PAGE_FAULT,
 };
 
-static inline int notify_die(enum die_val val,char *str,struct pt_regs *regs,long err,int trap, int sig)
+static inline int notify_die(enum die_val val, const char *str,
+                       struct pt_regs *regs, long err, int trap, int sig)
 {
-       struct die_args args = { .regs=regs, .str=str, .err=err, .trapnr=trap,.signr=sig };
+       struct die_args args = {
+               .regs = regs,
+               .str = str,
+               .err = err,
+               .trapnr = trap,
+               .signr = sig
+       };
        return notifier_call_chain(&i386die_chain, val, &args);
 }