Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull core debug changes from Ingo Molnar:
 "This contains mostly kernel debugging related updates:

   - make hung_task detection more configurable to distros
   - add final bits for x86 UV NMI debugging, with related KGDB changes
   - update the mailing-list of MAINTAINERS entries I'm involved with"

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  hung_task: Display every hung task warning
  sysctl: Add neg_one as a standard constraint
  x86/uv/nmi, kgdb/kdb: Fix UV NMI handler when KDB not configured
  x86/uv/nmi: Fix Sparse warnings
  kgdb/kdb: Fix no KDB config problem
  MAINTAINERS: Restore "L: linux-kernel@vger.kernel.org" entries

11 files changed, 116 insertions, 32 deletions

diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index ee9a2f983b99..e55124e7c40c 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -33,6 +33,10 @@ show up in /proc/sys/kernel:
 - domainname
 - hostname
 - hotplug
+- hung_task_panic
+- hung_task_check_count
+- hung_task_timeout_secs
+- hung_task_warnings
 - kexec_load_disabled
 - kptr_restrict
 - kstack_depth_to_print       [ X86 only ]
@@ -288,6 +292,44 @@ Default value is "/sbin/hotplug".
 
 ==============================================================
 
+hung_task_panic:
+
+Controls the kernel's behavior when a hung task is detected.
+This file shows up if CONFIG_DETECT_HUNG_TASK is enabled.
+
+0: continue operation. This is the default behavior.
+
+1: panic immediately.
+
+==============================================================
+
+hung_task_check_count:
+
+The upper bound on the number of tasks that are checked.
+This file shows up if CONFIG_DETECT_HUNG_TASK is enabled.
+
+==============================================================
+
+hung_task_timeout_secs:
+
+Check interval. When a task in D state did not get scheduled
+for more than this value report a warning.
+This file shows up if CONFIG_DETECT_HUNG_TASK is enabled.
+
+0: means infinite timeout - no checking done.
+
+==============================================================
+
+hung_task_warning:
+
+The maximum number of warnings to report. During a check interval
+When this value is reached, no more the warnings will be reported.
+This file shows up if CONFIG_DETECT_HUNG_TASK is enabled.
+
+-1: report an infinite number of warnings.
+
+==============================================================
+
 kexec_load_disabled:
 
 A toggle indicating if the kexec_load syscall has been disabled. This
diff --git a/MAINTAINERS b/MAINTAINERS
index 5f840aeab64d..6fb8759f49de 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2222,6 +2222,7 @@ F:	include/linux/clk.h
 CLOCKSOURCE, CLOCKEVENT DRIVERS
 M:      Daniel Lezcano <daniel.lezcano@linaro.org>
 M:      Thomas Gleixner <tglx@linutronix.de>
+L:      linux-kernel@vger.kernel.org
 T:      git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers/core
 S:      Supported
 F:      drivers/clocksource
@@ -4023,6 +4024,7 @@ F:	include/uapi/linux/hid*
 
 HIGH-RESOLUTION TIMERS, CLOCKEVENTS, DYNTICKS
 M:      Thomas Gleixner <tglx@linutronix.de>
+L:      linux-kernel@vger.kernel.org
 T:      git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers/core
 S:      Maintained
 F:      Documentation/timers/
@@ -4694,6 +4696,7 @@ F:	net/irda/
 
 IRQ SUBSYSTEM
 M:      Thomas Gleixner <tglx@linutronix.de>
+L:      linux-kernel@vger.kernel.org
 S:      Maintained
 T:      git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git irq/core
 F:      kernel/irq/
@@ -5325,6 +5328,7 @@ F:	drivers/media/usb/dvb-usb-v2/lmedm04*
 LOCKDEP AND LOCKSTAT
 M:      Peter Zijlstra <peterz@infradead.org>
 M:      Ingo Molnar <mingo@redhat.com>
+L:      linux-kernel@vger.kernel.org
 T:      git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git core/locking
 S:      Maintained
 F:      Documentation/lockdep*.txt
@@ -6622,6 +6626,7 @@ M:	Peter Zijlstra <a.p.zijlstra@chello.nl>
 M:      Paul Mackerras <paulus@samba.org>
 M:      Ingo Molnar <mingo@redhat.com>
 M:      Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
+L:      linux-kernel@vger.kernel.org
 T:      git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git perf/core
 S:      Supported
 F:      kernel/events/*
@@ -6745,6 +6750,7 @@ F:	drivers/scsi/pm8001/
 
 POSIX CLOCKS and TIMERS
 M:      Thomas Gleixner <tglx@linutronix.de>
+L:      linux-kernel@vger.kernel.org
 T:      git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers/core
 S:      Supported
 F:      fs/timerfd.c
@@ -7153,6 +7159,7 @@ F:	drivers/net/wireless/ray*
 RCUTORTURE MODULE
 M:      Josh Triplett <josh@freedesktop.org>
 M:      "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
+L:      linux-kernel@vger.kernel.org
 S:      Supported
 T:      git git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
 F:      Documentation/RCU/torture.txt
@@ -7160,6 +7167,7 @@ F:	kernel/rcu/torture.c
 
 RCUTORTURE TEST FRAMEWORK
 M:      "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
+L:      linux-kernel@vger.kernel.org
 S:      Supported
 T:      git git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
 F:      tools/testing/selftests/rcutorture
@@ -7183,6 +7191,7 @@ F:	net/rds/
 READ-COPY UPDATE (RCU)
 M:      Dipankar Sarma <dipankar@in.ibm.com>
 M:      "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
+L:      linux-kernel@vger.kernel.org
 W:      http://www.rdrop.com/users/paulmck/RCU/
 S:      Supported
 T:      git git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
@@ -7492,6 +7501,7 @@ F:	drivers/mmc/host/dw_mmc*
 TIMEKEEPING, CLOCKSOURCE CORE, NTP
 M:      John Stultz <john.stultz@linaro.org>
 M:      Thomas Gleixner <tglx@linutronix.de>
+L:      linux-kernel@vger.kernel.org
 T:      git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers/core
 S:      Supported
 F:      include/linux/clocksource.h
@@ -7517,6 +7527,7 @@ F:	drivers/watchdog/sc1200wdt.c
 SCHEDULER
 M:      Ingo Molnar <mingo@redhat.com>
 M:      Peter Zijlstra <peterz@infradead.org>
+L:      linux-kernel@vger.kernel.org
 T:      git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git sched/core
 S:      Maintained
 F:      kernel/sched/
@@ -7884,6 +7895,7 @@ F:	mm/sl?b.c
 SLEEPABLE READ-COPY UPDATE (SRCU)
 M:      Lai Jiangshan <laijs@cn.fujitsu.com>
 M:      "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
+L:      linux-kernel@vger.kernel.org
 W:      http://www.rdrop.com/users/paulmck/RCU/
 S:      Supported
 T:      git git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
@@ -9587,6 +9599,7 @@ M:	Thomas Gleixner <tglx@linutronix.de>
 M:      Ingo Molnar <mingo@redhat.com>
 M:      "H. Peter Anvin" <hpa@zytor.com>
 M:      x86@kernel.org
+L:      linux-kernel@vger.kernel.org
 T:      git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/core
 S:      Maintained
 F:      Documentation/x86/
diff --git a/arch/x86/include/asm/uv/uv.h b/arch/x86/include/asm/uv/uv.h
index 6b964a0b86d1..062921ef34e9 100644
--- a/arch/x86/include/asm/uv/uv.h
+++ b/arch/x86/include/asm/uv/uv.h
@@ -12,7 +12,6 @@ extern enum uv_system_type get_uv_system_type(void);
 extern int is_uv_system(void);
 extern void uv_cpu_init(void);
 extern void uv_nmi_init(void);
-extern void uv_register_nmi_notifier(void);
 extern void uv_system_init(void);
 extern const struct cpumask *uv_flush_tlb_others(const struct cpumask *cpumask,
                                                  struct mm_struct *mm,
@@ -26,7 +25,6 @@ static inline enum uv_system_type get_uv_system_type(void) { return UV_NONE; }
 static inline int is_uv_system(void)    { return 0; }
 static inline void uv_cpu_init(void)    { }
 static inline void uv_system_init(void) { }
-static inline void uv_register_nmi_notifier(void) { }
 static inline const struct cpumask *
 uv_flush_tlb_others(const struct cpumask *cpumask, struct mm_struct *mm,
                     unsigned long start, unsigned long end, unsigned int cpu)
diff --git a/arch/x86/kernel/apic/x2apic_uv_x.c b/arch/x86/kernel/apic/x2apic_uv_x.c
index ad0dc0428baf..d263b1307de1 100644
--- a/arch/x86/kernel/apic/x2apic_uv_x.c
+++ b/arch/x86/kernel/apic/x2apic_uv_x.c
@@ -980,7 +980,6 @@ void __init uv_system_init(void)
         uv_nmi_setup();
         uv_cpu_init();
         uv_scir_register_cpu_notifier();
-        uv_register_nmi_notifier();
         proc_mkdir("sgi_uv", NULL);
 
         /* register Legacy VGA I/O redirection handler */
diff --git a/arch/x86/platform/uv/uv_nmi.c b/arch/x86/platform/uv/uv_nmi.c
index 8eeccba73130..be27da60dc8f 100644
--- a/arch/x86/platform/uv/uv_nmi.c
+++ b/arch/x86/platform/uv/uv_nmi.c
@@ -74,7 +74,6 @@ static atomic_t	uv_in_nmi;
 static atomic_t uv_nmi_cpu = ATOMIC_INIT(-1);
 static atomic_t uv_nmi_cpus_in_nmi = ATOMIC_INIT(-1);
 static atomic_t uv_nmi_slave_continue;
-static atomic_t uv_nmi_kexec_failed;
 static cpumask_var_t uv_nmi_cpu_mask;
 
 /* Values for uv_nmi_slave_continue */
@@ -149,7 +148,8 @@ module_param_named(retry_count, uv_nmi_retry_count, int, 0644);
  *  "dump"      - dump process stack for each cpu
  *  "ips"       - dump IP info for each cpu
  *  "kdump"     - do crash dump
- *  "kdb"       - enter KDB/KGDB (default)
+ *  "kdb"       - enter KDB (default)
+ *  "kgdb"      - enter KGDB
  */
 static char uv_nmi_action[8] = "kdb";
 module_param_string(action, uv_nmi_action, sizeof(uv_nmi_action), 0644);
@@ -504,6 +504,7 @@ static void uv_nmi_touch_watchdogs(void)
 }
 
 #if defined(CONFIG_KEXEC)
+static atomic_t uv_nmi_kexec_failed;
 static void uv_nmi_kdump(int cpu, int master, struct pt_regs *regs)
 {
         /* Call crash to dump system state */
@@ -537,18 +538,45 @@ static inline void uv_nmi_kdump(int cpu, int master, struct pt_regs *regs)
 }
 #endif /* !CONFIG_KEXEC */
 
+#ifdef CONFIG_KGDB
 #ifdef CONFIG_KGDB_KDB
-/* Call KDB from NMI handler */
-static void uv_call_kdb(int cpu, struct pt_regs *regs, int master)
+static inline int uv_nmi_kdb_reason(void)
 {
-        int ret;
+        return KDB_REASON_SYSTEM_NMI;
+}
+#else /* !CONFIG_KGDB_KDB */
+static inline int uv_nmi_kdb_reason(void)
+{
+        /* Insure user is expecting to attach gdb remote */
+        if (uv_nmi_action_is("kgdb"))
+                return 0;
+
+        pr_err("UV: NMI error: KDB is not enabled in this kernel\n");
+        return -1;
+}
+#endif /* CONFIG_KGDB_KDB */
 
+/*
+ * Call KGDB/KDB from NMI handler
+ *
+ * Note that if both KGDB and KDB are configured, then the action of 'kgdb' or
+ * 'kdb' has no affect on which is used.  See the KGDB documention for further
+ * information.
+ */
+static void uv_call_kgdb_kdb(int cpu, struct pt_regs *regs, int master)
+{
         if (master) {
+                int reason = uv_nmi_kdb_reason();
+                int ret;
+
+                if (reason < 0)
+                        return;
+
                 /* call KGDB NMI handler as MASTER */
-                ret = kgdb_nmicallin(cpu, X86_TRAP_NMI, regs,
-                                        &uv_nmi_slave_continue);
+                ret = kgdb_nmicallin(cpu, X86_TRAP_NMI, regs, reason,
+                                &uv_nmi_slave_continue);
                 if (ret) {
-                        pr_alert("KDB returned error, is kgdboc set?\n");
+                        pr_alert("KGDB returned error, is kgdboc set?\n");
                         atomic_set(&uv_nmi_slave_continue, SLAVE_EXIT);
                 }
         } else {
@@ -567,12 +595,12 @@ static void uv_call_kdb(int cpu, struct pt_regs *regs, int master)
         uv_nmi_sync_exit(master);
 }
 
-#else /* !CONFIG_KGDB_KDB */
-static inline void uv_call_kdb(int cpu, struct pt_regs *regs, int master)
+#else /* !CONFIG_KGDB */
+static inline void uv_call_kgdb_kdb(int cpu, struct pt_regs *regs, int master)
 {
-        pr_err("UV: NMI error: KGDB/KDB is not enabled in this kernel\n");
+        pr_err("UV: NMI error: KGDB is not enabled in this kernel\n");
 }
-#endif /* !CONFIG_KGDB_KDB */
+#endif /* !CONFIG_KGDB */
 
 /*
  * UV NMI handler
@@ -606,9 +634,9 @@ int uv_handle_nmi(unsigned int reason, struct pt_regs *regs)
         if (uv_nmi_action_is("ips") || uv_nmi_action_is("dump"))
                 uv_nmi_dump_state(cpu, regs, master);
 
-        /* Call KDB if enabled */
-        else if (uv_nmi_action_is("kdb"))
-                uv_call_kdb(cpu, regs, master);
+        /* Call KGDB/KDB if enabled */
+        else if (uv_nmi_action_is("kdb") || uv_nmi_action_is("kgdb"))
+                uv_call_kgdb_kdb(cpu, regs, master);
 
         /* Clear per_cpu "in nmi" flag */
         atomic_set(&uv_cpu_nmi.state, UV_NMI_STATE_OUT);
@@ -634,7 +662,7 @@ int uv_handle_nmi(unsigned int reason, struct pt_regs *regs)
 /*
  * NMI handler for pulling in CPUs when perf events are grabbing our NMI
  */
-int uv_handle_nmi_ping(unsigned int reason, struct pt_regs *regs)
+static int uv_handle_nmi_ping(unsigned int reason, struct pt_regs *regs)
 {
         int ret;
 
@@ -651,7 +679,7 @@ int uv_handle_nmi_ping(unsigned int reason, struct pt_regs *regs)
         return ret;
 }
 
-void uv_register_nmi_notifier(void)
+static void uv_register_nmi_notifier(void)
 {
         if (register_nmi_handler(NMI_UNKNOWN, uv_handle_nmi, 0, "uv"))
                 pr_warn("UV: NMI handler failed to register\n");
@@ -695,6 +723,5 @@ void uv_nmi_setup(void)
                 uv_hub_nmi_per(cpu) = uv_hub_nmi_list[nid];
         }
         BUG_ON(!alloc_cpumask_var(&uv_nmi_cpu_mask, GFP_KERNEL));
+        uv_register_nmi_notifier();
 }
-
-
diff --git a/include/linux/kgdb.h b/include/linux/kgdb.h
index dfb4f2ffdaa2..6b06d378f3df 100644
--- a/include/linux/kgdb.h
+++ b/include/linux/kgdb.h
@@ -310,7 +310,8 @@ extern int
 kgdb_handle_exception(int ex_vector, int signo, int err_code,
                       struct pt_regs *regs);
 extern int kgdb_nmicallback(int cpu, void *regs);
-extern int kgdb_nmicallin(int cpu, int trapnr, void *regs, atomic_t *snd_rdy);
+extern int kgdb_nmicallin(int cpu, int trapnr, void *regs, int err_code,
+                          atomic_t *snd_rdy);
 extern void gdbstub_exit(int status);
 
 extern int                      kgdb_single_step;
diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h
index b13cf430764f..8045a554cafb 100644
--- a/include/linux/sched/sysctl.h
+++ b/include/linux/sched/sysctl.h
@@ -5,7 +5,7 @@
 extern int           sysctl_hung_task_check_count;
 extern unsigned int  sysctl_hung_task_panic;
 extern unsigned long sysctl_hung_task_timeout_secs;
-extern unsigned long sysctl_hung_task_warnings;
+extern int sysctl_hung_task_warnings;
 extern int proc_dohung_task_timeout_secs(struct ctl_table *table, int write,
                                          void __user *buffer,
                                          size_t *lenp, loff_t *ppos);
diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c
index 7d2f35e5df2f..334b3980ffc1 100644
--- a/kernel/debug/debug_core.c
+++ b/kernel/debug/debug_core.c
@@ -736,7 +736,8 @@ int kgdb_nmicallback(int cpu, void *regs)
         return 1;
 }
 
-int kgdb_nmicallin(int cpu, int trapnr, void *regs, atomic_t *send_ready)
+int kgdb_nmicallin(int cpu, int trapnr, void *regs, int err_code,
+                                                        atomic_t *send_ready)
 {
 #ifdef CONFIG_SMP
         if (!kgdb_io_ready(0) || !send_ready)
@@ -750,7 +751,7 @@ int kgdb_nmicallin(int cpu, int trapnr, void *regs, atomic_t *send_ready)
                 ks->cpu                 = cpu;
                 ks->ex_vector           = trapnr;
                 ks->signo               = SIGTRAP;
-                ks->err_code            = KGDB_KDB_REASON_SYSTEM_NMI;
+                ks->err_code            = err_code;
                 ks->linux_regs          = regs;
                 ks->send_ready          = send_ready;
                 kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
diff --git a/kernel/debug/debug_core.h b/kernel/debug/debug_core.h
index 572aa4f5677c..127d9bc49fb4 100644
--- a/kernel/debug/debug_core.h
+++ b/kernel/debug/debug_core.h
@@ -75,13 +75,11 @@ extern int kdb_stub(struct kgdb_state *ks);
 extern int kdb_parse(const char *cmdstr);
 extern int kdb_common_init_state(struct kgdb_state *ks);
 extern int kdb_common_deinit_state(void);
-#define KGDB_KDB_REASON_SYSTEM_NMI KDB_REASON_SYSTEM_NMI
 #else /* ! CONFIG_KGDB_KDB */
 static inline int kdb_stub(struct kgdb_state *ks)
 {
         return DBG_PASS_EVENT;
 }
-#define KGDB_KDB_REASON_SYSTEM_NMI 0
 #endif /* CONFIG_KGDB_KDB */
 
 #endif /* _DEBUG_CORE_H_ */
diff --git a/kernel/hung_task.c b/kernel/hung_task.c
index 9328b80eaf14..0b9c169d577f 100644
--- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -37,7 +37,7 @@ int __read_mostly sysctl_hung_task_check_count = PID_MAX_LIMIT;
  */
 unsigned long __read_mostly sysctl_hung_task_timeout_secs = CONFIG_DEFAULT_HUNG_TASK_TIMEOUT;
 
-unsigned long __read_mostly sysctl_hung_task_warnings = 10;
+int __read_mostly sysctl_hung_task_warnings = 10;
 
 static int __read_mostly did_panic;
 
@@ -98,7 +98,9 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
 
         if (!sysctl_hung_task_warnings)
                 return;
-        sysctl_hung_task_warnings--;
+
+        if (sysctl_hung_task_warnings > 0)
+                sysctl_hung_task_warnings--;
 
         /*
          * Ok, the task did not get scheduled for more than 2 minutes,
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 096db7452cbd..49e13e1f8fe6 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -121,6 +121,8 @@ extern int blk_iopoll_enabled;
 static int sixty = 60;
 #endif
 
+static int __maybe_unused neg_one = -1;
+
 static int zero;
 static int __maybe_unused one = 1;
 static int __maybe_unused two = 2;
@@ -997,9 +999,10 @@ static struct ctl_table kern_table[] = {
         {
                 .procname       = "hung_task_warnings",
                 .data           = &sysctl_hung_task_warnings,
-                .maxlen         = sizeof(unsigned long),
+                .maxlen         = sizeof(int),
                 .mode           = 0644,
-                .proc_handler   = proc_doulongvec_minmax,
+                .proc_handler   = proc_dointvec_minmax,
+                .extra1         = &neg_one,
         },
 #endif
 #ifdef CONFIG_COMPAT