[RFC PATCH 15/23] kernel/watchdog: Add a function to obtain the watchdog_allowed_mask

From: Ricardo Neri
Date: Tue Jun 12 2018 - 21:04:12 EST

Implementations of NMI watchdogs that use a single piece of hardware to
monitor all the CPUs in the system (as opposed to per-CPU implementations
such as perf) need to know which CPUs the watchdog is allowed to monitor.
In this manner, non-maskable interrupts are directed only to the monitored

Cc: Ashok Raj <ashok.raj@xxxxxxxxx>
Cc: Andi Kleen <andi.kleen@xxxxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: Jacob Pan <jacob.jun.pan@xxxxxxxxx>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@xxxxxxxxx>
Cc: Don Zickus <dzickus@xxxxxxxxxx>
Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Frederic Weisbecker <frederic@xxxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
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Cc: Paul Mackerras <paulus@xxxxxxxxx>
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Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
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Cc: Colin Ian King <colin.king@xxxxxxxxxxxxx>
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Cc: "Luis R. Rodriguez" <mcgrof@xxxxxxxxxx>
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Cc: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: "Ravi V. Shankar" <ravi.v.shankar@xxxxxxxxx>
Cc: x86@xxxxxxxxxx
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
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Signed-off-by: Ricardo Neri <ricardo.neri-calderon@xxxxxxxxxxxxxxx>
include/linux/nmi.h | 1 +
kernel/watchdog.c | 7 ++++++-
2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/include/linux/nmi.h b/include/linux/nmi.h
index e61b441..e608762 100644
--- a/include/linux/nmi.h
+++ b/include/linux/nmi.h
@@ -77,6 +77,7 @@ static inline void reset_hung_task_detector(void) { }

extern void hardlockup_detector_disable(void);
+extern struct cpumask *watchdog_get_allowed_cpumask(void);
extern unsigned int hardlockup_panic;
static inline void hardlockup_detector_disable(void) {}
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 5057376..b94bbe3 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -50,7 +50,7 @@ int __read_mostly nmi_watchdog_available;

static struct nmi_watchdog_ops *nmi_wd_ops;

-struct cpumask watchdog_allowed_mask __read_mostly;
+static struct cpumask watchdog_allowed_mask __read_mostly;

struct cpumask watchdog_cpumask __read_mostly;
unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
@@ -98,6 +98,11 @@ static int __init hardlockup_all_cpu_backtrace_setup(char *str)
__setup("hardlockup_all_cpu_backtrace=", hardlockup_all_cpu_backtrace_setup);
# endif /* CONFIG_SMP */
+struct cpumask *watchdog_get_allowed_cpumask(void)
+ return &watchdog_allowed_mask;