[PATCH 29/30] powerpc: ps3, pseries: Avoid duplicate call to kmsg_dump() on panic

[Guilherme G. Piccoli]

Currently both pseries and ps3 are platforms that define special
panic notifiers that run as callbacks inside powerpc generic panic
notifier. In both cases kmsg_dump() is called, and the reason seems
to be that both of these callbacks aims to effectively stop the
machine, so nothing would execute after that - hence, both force
a series of console flushing related operations, after calling
the kmsg dumpers.

Happens that recently the panic path was refactored, and now
kmsg_dump() is *certainly* called before the pre_reboot panic
notifiers, category in which both pseries/ps3 callbacks belong.
In other words: kmsg_dump() will execute twice in both platforms,
on panic path.

This patch prevents that by disabling the kmsg_dump() for both
platform's notifiers. But worth to notice that PowerNV still
has a legit use for executing kmsg_dump() in its unrecoverable
error path, so we rely in parameter passing to differentiate
both cases. Also, since the pre_reboot notifiers still run
earlier than console flushing routines, we kept that for
both pseries and ps3 platforms, only skipping kmsg_dump().

Fixes: 35adacd6fc48 ("powerpc/pseries, ps3: panic flush kernel messages before halting system")
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Hari Bathini <hbathini@xxxxxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Signed-off-by: Guilherme G. Piccoli <gpiccoli@xxxxxxxxxx>
---

We'd like to thanks specially the MiniCloud infrastructure [0] maintainers,
that allow us to test PowerPC code in a very complete, functional and FREE
environment.

[0] https://openpower.ic.unicamp.br/minicloud

 arch/powerpc/include/asm/bug.h         | 2 +-
 arch/powerpc/kernel/traps.c            | 6 ++++--
 arch/powerpc/platforms/powernv/opal.c  | 2 +-
 arch/powerpc/platforms/ps3/setup.c     | 2 +-
 arch/powerpc/platforms/pseries/setup.c | 2 +-
 5 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/include/asm/bug.h b/arch/powerpc/include/asm/bug.h
index ecbae1832de3..49e5f6f86869 100644
--- a/arch/powerpc/include/asm/bug.h
+++ b/arch/powerpc/include/asm/bug.h
@@ -166,7 +166,7 @@ extern void die(const char *, struct pt_regs *, long);
 void die_mce(const char *str, struct pt_regs *regs, long err);
 extern bool die_will_crash(void);
 extern void panic_flush_kmsg_start(void);
-extern void panic_flush_kmsg_end(void);
+extern void panic_flush_kmsg_end(bool dump);
 #endif /* !__ASSEMBLY__ */
 
 #endif /* __KERNEL__ */
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index a08bb7cefdc5..837a5ed98d62 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -169,9 +169,11 @@ extern void panic_flush_kmsg_start(void)
 	bust_spinlocks(1);
 }
 
-extern void panic_flush_kmsg_end(void)
+extern void panic_flush_kmsg_end(bool dump)
 {
-	kmsg_dump(KMSG_DUMP_PANIC);
+	if (dump)
+		kmsg_dump(KMSG_DUMP_PANIC);
+
 	bust_spinlocks(0);
 	debug_locks_off();
 	console_flush_on_panic(CONSOLE_FLUSH_PENDING);
diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
index 55a8fbfdb5b2..d172ceedece2 100644
--- a/arch/powerpc/platforms/powernv/opal.c
+++ b/arch/powerpc/platforms/powernv/opal.c
@@ -641,7 +641,7 @@ void __noreturn pnv_platform_error_reboot(struct pt_regs *regs, const char *msg)
 		show_regs(regs);
 	smp_send_stop();
 
-	panic_flush_kmsg_end();
+	panic_flush_kmsg_end(true);
 
 	/*
 	 * Don't bother to shut things down because this will
diff --git a/arch/powerpc/platforms/ps3/setup.c b/arch/powerpc/platforms/ps3/setup.c
index 3de9145c20bc..7cb78e508fb3 100644
--- a/arch/powerpc/platforms/ps3/setup.c
+++ b/arch/powerpc/platforms/ps3/setup.c
@@ -102,7 +102,7 @@ static void ps3_panic(char *str)
 	printk("   System does not reboot automatically.\n");
 	printk("   Please press POWER button.\n");
 	printk("\n");
-	panic_flush_kmsg_end();
+	panic_flush_kmsg_end(false);
 
 	while(1)
 		lv1_pause(1);
diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index 955ff8aa1644..d6eea473eafd 100644
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -856,7 +856,7 @@ static void __init pSeries_setup_arch(void)
 
 static void pseries_panic(char *str)
 {
-	panic_flush_kmsg_end();
+	panic_flush_kmsg_end(false);
 	rtas_os_term(str);
 }
 
-- 
2.36.0