Commit-ID: 34ddaa3e5c0096fef52485186c7eb6cf56ddc686
Gitweb: https://git.kernel.org/tip/34ddaa3e5c0096fef52485186c7eb6cf56ddc686
Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Tue, 3 Oct 2017 16:39:02 +0200
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Wed, 4 Oct 2017 10:53:54 +0200
powerpc/watchdog: Make use of watchdog_nmi_probe()
The rework of the core hotplug code triggers the WARN_ON in start_wd_cpu()
on powerpc because it is called multiple times for the boot CPU.
The first call is via:
start_wd_on_cpu+0x80/0x2f0
watchdog_nmi_reconfigure+0x124/0x170
softlockup_reconfigure_threads+0x110/0x130
lockup_detector_init+0xbc/0xe0
kernel_init_freeable+0x18c/0x37c
kernel_init+0x2c/0x160
ret_from_kernel_thread+0x5c/0xbc
And then again via the CPU hotplug registration:
start_wd_on_cpu+0x80/0x2f0
cpuhp_invoke_callback+0x194/0x620
cpuhp_thread_fun+0x7c/0x1b0
smpboot_thread_fn+0x290/0x2a0
kthread+0x168/0x1b0
ret_from_kernel_thread+0x5c/0xbc
This can be avoided by setting up the cpu hotplug state with nocalls and
move the initialization to the watchdog_nmi_probe() function. That
initializes the hotplug callbacks without invoking the callback and the
following core initialization function then configures the watchdog for the
online CPUs (in this case CPU0) via softlockup_reconfigure_threads().
Reported-and-tested-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Acked-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
---
arch/powerpc/kernel/watchdog.c | 17 ++++++++---------
include/linux/nmi.h | 1 +
kernel/watchdog.c | 5 ++++-
3 files changed, 13 insertions(+), 10 deletions(-)
diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c
index f9b4c63..c702a89 100644
--- a/arch/powerpc/kernel/watchdog.c
+++ b/arch/powerpc/kernel/watchdog.c
@@ -373,22 +373,21 @@ void watchdog_nmi_start(void)
}
/*
- * This runs after lockup_detector_init() which sets up watchdog_cpumask.
+ * Invoked from core watchdog init.
*/
-static int __init powerpc_watchdog_init(void)
+int __init watchdog_nmi_probe(void)
{
int err;
- watchdog_calc_timeouts();
-
- err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "powerpc/watchdog:online",
- start_wd_on_cpu, stop_wd_on_cpu);
- if (err < 0)
+ err = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
+ "powerpc/watchdog:online",
+ start_wd_on_cpu, stop_wd_on_cpu);
+ if (err < 0) {
pr_warn("Watchdog could not be initialized");
-
+ return err;
+ }
return 0;
}
-arch_initcall(powerpc_watchdog_init);
static void handle_backtrace_ipi(struct pt_regs *regs)
{
diff --git a/include/linux/nmi.h b/include/linux/nmi.h
index 0c9ed49..27e249e 100644
--- a/include/linux/nmi.h
+++ b/include/linux/nmi.h
@@ -111,6 +111,7 @@ static inline int hardlockup_detector_perf_init(void) { return 0; }
void watchdog_nmi_stop(void);
void watchdog_nmi_start(void);
+int watchdog_nmi_probe(void);
/**
* touch_nmi_watchdog - restart NMI watchdog timeout.
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index fff90fe..5c6fb7c 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -608,7 +608,6 @@ static inline int watchdog_park_threads(void) { return 0; }
static inline void watchdog_unpark_threads(void) { }
static inline int watchdog_enable_all_cpus(void) { return 0; }
static inline void watchdog_disable_all_cpus(void) { }
-static inline void softlockup_init_threads(void) { }
static void softlockup_reconfigure_threads(void)
{
cpus_read_lock();
@@ -617,6 +616,10 @@ static void softlockup_reconfigure_threads(void)
watchdog_nmi_start();
cpus_read_unlock();
}
+static inline void softlockup_init_threads(void)
+{
+ softlockup_reconfigure_threads();
+}
#endif /* !CONFIG_SOFTLOCKUP_DETECTOR */
static void __lockup_detector_cleanup(void)
--
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