mips/panic: replace smp_send_stop() with kdump friendly version in panic path

Daniel Walker reported problems which happens when
crash_kexec_post_notifiers kernel option is enabled
(https://lkml.org/lkml/2015/6/24/44).

In that case, smp_send_stop() is called before entering kdump routines
which assume other CPUs are still online.  As the result, kdump
routines fail to save other CPUs' registers.  Additionally for MIPS
OCTEON, it misses to stop the watchdog timer.

To fix this problem, call a new kdump friendly function,
crash_smp_send_stop(), instead of the smp_send_stop() when
crash_kexec_post_notifiers is enabled.  crash_smp_send_stop() is a
weak function, and it just call smp_send_stop().  Architecture
codes should override it so that kdump can work appropriately.
This patch provides MIPS version.

Fixes: f06e5153f4ae (kernel/panic.c: add "crash_kexec_post_notifiers" option)
Link: http://lkml.kernel.org/r/20160810080950.11028.28000.stgit@sysi4-13.yrl.intra.hitachi.co.jp
Signed-off-by: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
Reported-by: Daniel Walker <dwalker@fifo99.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Daniel Walker <dwalker@fifo99.com>
Cc: Xunlei Pang <xpang@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: David Daney <david.daney@cavium.com>
Cc: Aaro Koskinen <aaro.koskinen@iki.fi>
Cc: "Steven J. Hill" <steven.hill@cavium.com>
Cc: Corey Minyard <cminyard@mvista.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 33 insertions, 1 deletions

diff --git a/arch/mips/cavium-octeon/setup.c b/arch/mips/cavium-octeon/setup.c
index cb16fcc5f8f0..5537f95b28c9 100644
--- a/arch/mips/cavium-octeon/setup.c
+++ b/arch/mips/cavium-octeon/setup.c
@@ -267,6 +267,17 @@ static void octeon_crash_shutdown(struct pt_regs *regs)
 	default_machine_crash_shutdown(regs);
 }
 
+#ifdef CONFIG_SMP
+void octeon_crash_smp_send_stop(void)
+{
+	int cpu;
+
+	/* disable watchdogs */
+	for_each_online_cpu(cpu)
+		cvmx_write_csr(CVMX_CIU_WDOGX(cpu_logical_map(cpu)), 0);
+}
+#endif
+
 #endif /* CONFIG_KEXEC */
 
 #ifdef CONFIG_CAVIUM_RESERVE32
@@ -911,6 +922,9 @@ void __init prom_init(void)
 	_machine_kexec_shutdown = octeon_shutdown;
 	_machine_crash_shutdown = octeon_crash_shutdown;
 	_machine_kexec_prepare = octeon_kexec_prepare;
+#ifdef CONFIG_SMP
+	_crash_smp_send_stop = octeon_crash_smp_send_stop;
+#endif
 #endif
 
 	octeon_user_io_init();
diff --git a/arch/mips/include/asm/kexec.h b/arch/mips/include/asm/kexec.h
index ee25ebbf2a28..493a3cc7c39a 100644
--- a/arch/mips/include/asm/kexec.h
+++ b/arch/mips/include/asm/kexec.h
@@ -45,6 +45,7 @@ extern const unsigned char kexec_smp_wait[];
 extern unsigned long secondary_kexec_args[4];
 extern void (*relocated_kexec_smp_wait) (void *);
 extern atomic_t kexec_ready_to_reboot;
+extern void (*_crash_smp_send_stop)(void);
 #endif
 #endif
 
diff --git a/arch/mips/kernel/crash.c b/arch/mips/kernel/crash.c
index 610f0f3bdb34..1723b1762297 100644
--- a/arch/mips/kernel/crash.c
+++ b/arch/mips/kernel/crash.c
@@ -47,9 +47,14 @@ static void crash_shutdown_secondary(void *passed_regs)
 
 static void crash_kexec_prepare_cpus(void)
 {
+	static int cpus_stopped;
 	unsigned int msecs;
+	unsigned int ncpus;
 
-	unsigned int ncpus = num_online_cpus() - 1;/* Excluding the panic cpu */
+	if (cpus_stopped)
+		return;
+
+	ncpus = num_online_cpus() - 1;/* Excluding the panic cpu */
 
 	dump_send_ipi(crash_shutdown_secondary);
 	smp_wmb();
@@ -64,6 +69,17 @@ static void crash_kexec_prepare_cpus(void)
 		cpu_relax();
 		mdelay(1);
 	}
+
+	cpus_stopped = 1;
+}
+
+/* Override the weak function in kernel/panic.c */
+void crash_smp_send_stop(void)
+{
+	if (_crash_smp_send_stop)
+		_crash_smp_send_stop();
+
+	crash_kexec_prepare_cpus();
 }
 
 #else /* !defined(CONFIG_SMP)  */
diff --git a/arch/mips/kernel/machine_kexec.c b/arch/mips/kernel/machine_kexec.c
index 50980bf3983e..59725204105c 100644
--- a/arch/mips/kernel/machine_kexec.c
+++ b/arch/mips/kernel/machine_kexec.c
@@ -25,6 +25,7 @@ void (*_machine_crash_shutdown)(struct pt_regs *regs) = NULL;
 #ifdef CONFIG_SMP
 void (*relocated_kexec_smp_wait) (void *);
 atomic_t kexec_ready_to_reboot = ATOMIC_INIT(0);
+void (*_crash_smp_send_stop)(void) = NULL;
 #endif
 
 int