nmi_backtrace: add more trigger_*_cpu_backtrace() methods

Patch series "improvements to the nmi_backtrace code" v9.

This patch series modifies the trigger_xxx_backtrace() NMI-based remote
backtracing code to make it more flexible, and makes a few small
improvements along the way.

The motivation comes from the task isolation code, where there are
scenarios where we want to be able to diagnose a case where some cpu is
about to interrupt a task-isolated cpu.  It can be helpful to see both
where the interrupting cpu is, and also an approximation of where the
cpu that is being interrupted is.  The nmi_backtrace framework allows us
to discover the stack of the interrupted cpu.

I've tested that the change works as desired on tile, and build-tested
x86, arm, mips, and sparc64.  For x86 I confirmed that the generic
cpuidle stuff as well as the architecture-specific routines are in the
new cpuidle section.  For arm, mips, and sparc I just build-tested it
and made sure the generic cpuidle routines were in the new cpuidle
section, but I didn't attempt to figure out which the platform-specific
idle routines might be.  That might be more usefully done by someone
with platform experience in follow-up patches.

This patch (of 4):

Currently you can only request a backtrace of either all cpus, or all
cpus but yourself.  It can also be helpful to request a remote backtrace
of a single cpu, and since we want that, the logical extension is to
support a cpumask as the underlying primitive.

This change modifies the existing lib/nmi_backtrace.c code to take a
cpumask as its basic primitive, and modifies the linux/nmi.h code to use
the new "cpumask" method instead.

The existing clients of nmi_backtrace (arm and x86) are converted to
using the new cpumask approach in this change.

The other users of the backtracing API (sparc64 and mips) are converted
to use the cpumask approach rather than the all/allbutself approach.
The mips code ignored the "include_self" boolean but with this change it
will now also dump a local backtrace if requested.

Link: http://lkml.kernel.org/r/1472487169-14923-2-git-send-email-cmetcalf@mellanox.com
Signed-off-by: Chris Metcalf <cmetcalf@mellanox.com>
Tested-by: Daniel Thompson <daniel.thompson@linaro.org> [arm]
Reviewed-by: Aaron Tomlin <atomlin@redhat.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/arm/include/asm/irq.h b/arch/arm/include/asm/irq.h
index 1bd9510de1b9ced64b1947f2734ddbf4c8ce4f5d..e53638c8ed8aafc4dccfe9509c8284405d6fde2a 100644 (file)
--- a/arch/arm/include/asm/irq.h
+++ b/arch/arm/include/asm/irq.h
@@ -36,8 +36,9 @@ extern void set_handle_irq(void (*handle_irq)(struct pt_regs *));
 #endif
 
 #ifdef CONFIG_SMP
-extern void arch_trigger_all_cpu_backtrace(bool);
-#define arch_trigger_all_cpu_backtrace(x) arch_trigger_all_cpu_backtrace(x)
+extern void arch_trigger_cpumask_backtrace(const cpumask_t *mask,
+                                          bool exclude_self);
+#define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace
 #endif
 
 static inline int nr_legacy_irqs(void)

diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index 937c8920d741485a8992209a778a1ae385a93408..5abc5697e4e595f7126840696a9352aaf2da4657 100644 (file)
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -760,7 +760,7 @@ static void raise_nmi(cpumask_t *mask)
        smp_cross_call(mask, IPI_CPU_BACKTRACE);
 }
 
-void arch_trigger_all_cpu_backtrace(bool include_self)
+void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
 {
-       nmi_trigger_all_cpu_backtrace(include_self, raise_nmi);
+       nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_nmi);
 }

diff --git a/arch/mips/include/asm/irq.h b/arch/mips/include/asm/irq.h
index 15e0fecbc300fd9752023931984fe277a73da876..6bf10e796553838bbd165dc31e117fb1ae9e4234 100644 (file)
--- a/arch/mips/include/asm/irq.h
+++ b/arch/mips/include/asm/irq.h
@@ -51,7 +51,8 @@ extern int cp0_fdc_irq;
 
 extern int get_c0_fdc_int(void);
 
-void arch_trigger_all_cpu_backtrace(bool);
-#define arch_trigger_all_cpu_backtrace arch_trigger_all_cpu_backtrace
+void arch_trigger_cpumask_backtrace(const struct cpumask *mask,
+                                   bool exclude_self);
+#define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace
 
 #endif /* _ASM_IRQ_H */

diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
index d2d061520a23000116cc9c6d9f0a7f4a077aa372..9514e5f2209ff69eca82a21e6309ca54fc53c42a 100644 (file)
--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -569,9 +569,16 @@ static void arch_dump_stack(void *info)
        dump_stack();
 }
 
-void arch_trigger_all_cpu_backtrace(bool include_self)
+void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
 {
-       smp_call_function(arch_dump_stack, NULL, 1);
+       long this_cpu = get_cpu();
+
+       if (cpumask_test_cpu(this_cpu, mask) && !exclude_self)
+               dump_stack();
+
+       smp_call_function_many(mask, arch_dump_stack, NULL, 1);
+
+       put_cpu();
 }
 
 int mips_get_process_fp_mode(struct task_struct *task)

diff --git a/arch/sparc/include/asm/irq_64.h b/arch/sparc/include/asm/irq_64.h
index 3f70f900e834203f0974169ebe95380442486d1f..1d51a11fb261cc17a1b05796b6bed1934f1ff589 100644 (file)
--- a/arch/sparc/include/asm/irq_64.h
+++ b/arch/sparc/include/asm/irq_64.h
@@ -86,8 +86,9 @@ static inline unsigned long get_softint(void)
        return retval;
 }
 
-void arch_trigger_all_cpu_backtrace(bool);
-#define arch_trigger_all_cpu_backtrace arch_trigger_all_cpu_backtrace
+void arch_trigger_cpumask_backtrace(const struct cpumask *mask,
+                                   bool exclude_self);
+#define arch_trigger_cpumask_backtrace arch_trigger_cpumask_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 fa14402b33f95f34d7c9f84f26ef23ea7c05aff1..47ff5588e5213748d34bd4d6876eeefb779aca12 100644 (file)
--- a/arch/sparc/kernel/process_64.c
+++ b/arch/sparc/kernel/process_64.c
@@ -239,7 +239,7 @@ static void __global_reg_poll(struct global_reg_snapshot *gp)
        }
 }
 
-void arch_trigger_all_cpu_backtrace(bool include_self)
+void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
 {
        struct thread_info *tp = current_thread_info();
        struct pt_regs *regs = get_irq_regs();
@@ -255,15 +255,15 @@ void arch_trigger_all_cpu_backtrace(bool include_self)
 
        memset(global_cpu_snapshot, 0, sizeof(global_cpu_snapshot));
 
-       if (include_self)
+       if (cpumask_test_cpu(this_cpu, mask) && !exclude_self)
                __global_reg_self(tp, regs, this_cpu);
 
        smp_fetch_global_regs();
 
-       for_each_online_cpu(cpu) {
+       for_each_cpu(cpu, mask) {
                struct global_reg_snapshot *gp;
 
-               if (!include_self && cpu == this_cpu)
+               if (exclude_self && cpu == this_cpu)
                        continue;
 
                gp = &global_cpu_snapshot[cpu].reg;
@@ -300,7 +300,7 @@ void arch_trigger_all_cpu_backtrace(bool include_self)
 
 static void sysrq_handle_globreg(int key)
 {
-       arch_trigger_all_cpu_backtrace(true);
+       trigger_all_cpu_backtrace();
 }
 
 static struct sysrq_key_op sparc_globalreg_op = {

diff --git a/arch/x86/include/asm/irq.h b/arch/x86/include/asm/irq.h
index e7de5c9a4fbdd2c5d99b78d82d2c58019d20dc04..16d3fa211962809c4e879d049dbdb5dde4049702 100644 (file)
--- a/arch/x86/include/asm/irq.h
+++ b/arch/x86/include/asm/irq.h
@@ -50,8 +50,9 @@ extern int vector_used_by_percpu_irq(unsigned int vector);
 extern void init_ISA_irqs(void);
 
 #ifdef CONFIG_X86_LOCAL_APIC
-void arch_trigger_all_cpu_backtrace(bool);
-#define arch_trigger_all_cpu_backtrace arch_trigger_all_cpu_backtrace
+void arch_trigger_cpumask_backtrace(const struct cpumask *mask,
+                                   bool exclude_self);
+#define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace
 #endif
 
 #endif /* _ASM_X86_IRQ_H */

diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c
index f29501e1a5c131827527d41a517bd508484033ba..c73c9fb281e18f7d058fd69497f504adeb3147c1 100644 (file)
--- a/arch/x86/kernel/apic/hw_nmi.c
+++ b/arch/x86/kernel/apic/hw_nmi.c
@@ -26,32 +26,32 @@ u64 hw_nmi_get_sample_period(int watchdog_thresh)
 }
 #endif
 
-#ifdef arch_trigger_all_cpu_backtrace
+#ifdef arch_trigger_cpumask_backtrace
 static void nmi_raise_cpu_backtrace(cpumask_t *mask)
 {
        apic->send_IPI_mask(mask, NMI_VECTOR);
 }
 
-void arch_trigger_all_cpu_backtrace(bool include_self)
+void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
 {
-       nmi_trigger_all_cpu_backtrace(include_self, nmi_raise_cpu_backtrace);
+       nmi_trigger_cpumask_backtrace(mask, exclude_self,
+                                     nmi_raise_cpu_backtrace);
 }
 
-static int
-arch_trigger_all_cpu_backtrace_handler(unsigned int cmd, struct pt_regs *regs)
+static int nmi_cpu_backtrace_handler(unsigned int cmd, struct pt_regs *regs)
 {
        if (nmi_cpu_backtrace(regs))
                return NMI_HANDLED;
 
        return NMI_DONE;
 }
-NOKPROBE_SYMBOL(arch_trigger_all_cpu_backtrace_handler);
+NOKPROBE_SYMBOL(nmi_cpu_backtrace_handler);
 
-static int __init register_trigger_all_cpu_backtrace(void)
+static int __init register_nmi_cpu_backtrace_handler(void)
 {
-       register_nmi_handler(NMI_LOCAL, arch_trigger_all_cpu_backtrace_handler,
+       register_nmi_handler(NMI_LOCAL, nmi_cpu_backtrace_handler,
                                0, "arch_bt");
        return 0;
 }
-early_initcall(register_trigger_all_cpu_backtrace);
+early_initcall(register_nmi_cpu_backtrace_handler);
 #endif

diff --git a/include/linux/nmi.h b/include/linux/nmi.h
index 4630eeae18e08df43be6567ca5fbcb2027643c65..a78c35cff1ae34c9c80f0f4d57895df870528aba 100644 (file)
--- a/include/linux/nmi.h
+++ b/include/linux/nmi.h
@@ -35,21 +35,34 @@ static inline void hardlockup_detector_disable(void) {}
  * 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
+#ifdef arch_trigger_cpumask_backtrace
 static inline bool trigger_all_cpu_backtrace(void)
 {
-       arch_trigger_all_cpu_backtrace(true);
-
+       arch_trigger_cpumask_backtrace(cpu_online_mask, false);
        return true;
 }
+
 static inline bool trigger_allbutself_cpu_backtrace(void)
 {
-       arch_trigger_all_cpu_backtrace(false);
+       arch_trigger_cpumask_backtrace(cpu_online_mask, true);
+       return true;
+}
+
+static inline bool trigger_cpumask_backtrace(struct cpumask *mask)
+{
+       arch_trigger_cpumask_backtrace(mask, false);
+       return true;
+}
+
+static inline bool trigger_single_cpu_backtrace(int cpu)
+{
+       arch_trigger_cpumask_backtrace(cpumask_of(cpu), false);
        return true;
 }
 
 /* generic implementation */
-void nmi_trigger_all_cpu_backtrace(bool include_self,
+void nmi_trigger_cpumask_backtrace(const cpumask_t *mask,
+                                  bool exclude_self,
                                   void (*raise)(cpumask_t *mask));
 bool nmi_cpu_backtrace(struct pt_regs *regs);
 
@@ -62,6 +75,14 @@ static inline bool trigger_allbutself_cpu_backtrace(void)
 {
        return false;
 }
+static inline bool trigger_cpumask_backtrace(struct cpumask *mask)
+{
+       return false;
+}
+static inline bool trigger_single_cpu_backtrace(int cpu)
+{
+       return false;
+}
 #endif
 
 #ifdef CONFIG_LOCKUP_DETECTOR

diff --git a/lib/nmi_backtrace.c b/lib/nmi_backtrace.c
index 26caf51cc2383e80bc1902c6c65b66102e8d5af0..df347e355267b176330aabc746b88787032e88e3 100644 (file)
--- a/lib/nmi_backtrace.c
+++ b/lib/nmi_backtrace.c
@@ -17,20 +17,21 @@
 #include <linux/kprobes.h>
 #include <linux/nmi.h>
 
-#ifdef arch_trigger_all_cpu_backtrace
+#ifdef arch_trigger_cpumask_backtrace
 /* For reliability, we're prepared to waste bits here. */
 static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;
 
-/* "in progress" flag of arch_trigger_all_cpu_backtrace */
+/* "in progress" flag of arch_trigger_cpumask_backtrace */
 static unsigned long backtrace_flag;
 
 /*
- * When raise() is called it will be is passed a pointer to the
+ * When raise() is called it will be passed a pointer to the
  * backtrace_mask. Architectures that call nmi_cpu_backtrace()
  * directly from their raise() functions may rely on the mask
  * they are passed being updated as a side effect of this call.
  */
-void nmi_trigger_all_cpu_backtrace(bool include_self,
+void nmi_trigger_cpumask_backtrace(const cpumask_t *mask,
+                                  bool exclude_self,
                                   void (*raise)(cpumask_t *mask))
 {
        int i, this_cpu = get_cpu();
@@ -44,13 +45,13 @@ void nmi_trigger_all_cpu_backtrace(bool include_self,
                return;
        }
 
-       cpumask_copy(to_cpumask(backtrace_mask), cpu_online_mask);
-       if (!include_self)
+       cpumask_copy(to_cpumask(backtrace_mask), mask);
+       if (exclude_self)
                cpumask_clear_cpu(this_cpu, to_cpumask(backtrace_mask));
 
        if (!cpumask_empty(to_cpumask(backtrace_mask))) {
-               pr_info("Sending NMI to %s CPUs:\n",
-                       (include_self ? "all" : "other"));
+               pr_info("Sending NMI from CPU %d to CPUs %*pbl:\n",
+                       this_cpu, nr_cpumask_bits, to_cpumask(backtrace_mask));
                raise(to_cpumask(backtrace_mask));
        }