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Subject[tip:core/debug] debug lockups: Improve lockup detection, fix generic arch fallback
Commit-ID:  47cab6a722d44c71c4f8224017ef548522243cf4
Gitweb: http://git.kernel.org/tip/47cab6a722d44c71c4f8224017ef548522243cf4
Author: Ingo Molnar <mingo@elte.hu>
AuthorDate: Mon, 3 Aug 2009 09:31:54 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Mon, 3 Aug 2009 09:56:52 +0200

debug lockups: Improve lockup detection, fix generic arch fallback

As Andrew noted, my previous patch ("debug lockups: Improve lockup
detection") broke/removed SysRq-L support from architecture that do
not provide a __trigger_all_cpu_backtrace implementation.

Restore a fallback path and clean up the SysRq-L machinery a bit:

- Rename the arch method to arch_trigger_all_cpu_backtrace()

- Simplify the define

- Document the method a bit - in the hope of more architectures
adding support for it.

[ The patch touches Sparc code for the rename. ]

Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "David S. Miller" <davem@davemloft.net>
LKML-Reference: <20090802140809.7ec4bb6b.akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
arch/sparc/include/asm/irq_64.h | 4 ++--
arch/sparc/kernel/process_64.c | 4 ++--
arch/x86/include/asm/nmi.h | 4 ++--
arch/x86/kernel/apic/nmi.c | 2 +-
drivers/char/sysrq.c | 15 ++++++++++++++-
include/linux/nmi.h | 19 +++++++++++++++++--
6 files changed, 38 insertions(+), 10 deletions(-)
diff --git a/arch/sparc/include/asm/irq_64.h b/arch/sparc/include/asm/irq_64.h
index 1934f2c..a0b443c 100644
--- a/arch/sparc/include/asm/irq_64.h
+++ b/arch/sparc/include/asm/irq_64.h
@@ -89,8 +89,8 @@ static inline unsigned long get_softint(void)
return retval;
}

-void __trigger_all_cpu_backtrace(void);
-#define trigger_all_cpu_backtrace() __trigger_all_cpu_backtrace()
+void arch_trigger_all_cpu_backtrace(void);
+#define arch_trigger_all_cpu_backtrace arch_trigger_all_cpu_backtrace

extern void *hardirq_stack[NR_CPUS];
extern void *softirq_stack[NR_CPUS];
diff --git a/arch/sparc/kernel/process_64.c b/arch/sparc/kernel/process_64.c
index 4041f94..18d6785 100644
--- a/arch/sparc/kernel/process_64.c
+++ b/arch/sparc/kernel/process_64.c
@@ -251,7 +251,7 @@ static void __global_reg_poll(struct global_reg_snapshot *gp)
}
}

-void __trigger_all_cpu_backtrace(void)
+void arch_trigger_all_cpu_backtrace(void)
{
struct thread_info *tp = current_thread_info();
struct pt_regs *regs = get_irq_regs();
@@ -304,7 +304,7 @@ void __trigger_all_cpu_backtrace(void)

static void sysrq_handle_globreg(int key, struct tty_struct *tty)
{
- __trigger_all_cpu_backtrace();
+ arch_trigger_all_cpu_backtrace();
}

static struct sysrq_key_op sparc_globalreg_op = {
diff --git a/arch/x86/include/asm/nmi.h b/arch/x86/include/asm/nmi.h
index c86e5ed..e63cf7d 100644
--- a/arch/x86/include/asm/nmi.h
+++ b/arch/x86/include/asm/nmi.h
@@ -45,8 +45,8 @@ extern int proc_nmi_enabled(struct ctl_table *, int , struct file *,
void __user *, size_t *, loff_t *);
extern int unknown_nmi_panic;

-void __trigger_all_cpu_backtrace(void);
-#define trigger_all_cpu_backtrace() __trigger_all_cpu_backtrace()
+void arch_trigger_all_cpu_backtrace(void);
+#define arch_trigger_all_cpu_backtrace arch_trigger_all_cpu_backtrace

static inline void localise_nmi_watchdog(void)
{
diff --git a/arch/x86/kernel/apic/nmi.c b/arch/x86/kernel/apic/nmi.c
index 1bb1ac2..db72202 100644
--- a/arch/x86/kernel/apic/nmi.c
+++ b/arch/x86/kernel/apic/nmi.c
@@ -554,7 +554,7 @@ int do_nmi_callback(struct pt_regs *regs, int cpu)
return 0;
}

-void __trigger_all_cpu_backtrace(void)
+void arch_trigger_all_cpu_backtrace(void)
{
int i;

diff --git a/drivers/char/sysrq.c b/drivers/char/sysrq.c
index 165f307..50eecfe 100644
--- a/drivers/char/sysrq.c
+++ b/drivers/char/sysrq.c
@@ -223,7 +223,20 @@ static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);

static void sysrq_handle_showallcpus(int key, struct tty_struct *tty)
{
- trigger_all_cpu_backtrace();
+ /*
+ * Fall back to the workqueue based printing if the
+ * backtrace printing did not succeed or the
+ * architecture has no support for it:
+ */
+ if (!trigger_all_cpu_backtrace()) {
+ struct pt_regs *regs = get_irq_regs();
+
+ if (regs) {
+ printk(KERN_INFO "CPU%d:\n", smp_processor_id());
+ show_regs(regs);
+ }
+ schedule_work(&sysrq_showallcpus);
+ }
}

static struct sysrq_key_op sysrq_showallcpus_op = {
diff --git a/include/linux/nmi.h b/include/linux/nmi.h
index 29af2d5..b752e80 100644
--- a/include/linux/nmi.h
+++ b/include/linux/nmi.h
@@ -28,8 +28,23 @@ static inline void acpi_nmi_disable(void) { }
static inline void acpi_nmi_enable(void) { }
#endif

-#ifndef trigger_all_cpu_backtrace
-#define trigger_all_cpu_backtrace() do { } while (0)
+/*
+ * Create trigger_all_cpu_backtrace() out of the arch-provided
+ * base function. Return whether such support was available,
+ * to allow calling code to fall back to some other mechanism:
+ */
+#ifdef arch_trigger_all_cpu_backtrace
+static inline bool trigger_all_cpu_backtrace(void)
+{
+ arch_trigger_all_cpu_backtrace();
+
+ return true;
+}
+#else
+static inline bool trigger_all_cpu_backtrace(void)
+{
+ return false;
+}
#endif

#endif

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