From: Paul Burton <paul.burton@xxxxxxxx>
commit 5a267832c2ec47b2dad0fdb291a96bb5b8869315 upstream.
The generic nmi_cpu_backtrace() function calls show_regs() when a struct
pt_regs is available, and dump_stack() otherwise. If we were to make use
of the generic nmi_cpu_backtrace() with MIPS' current implementation of
show_regs() this would mean that we see only register data with no
accompanying stack information, in contrast with our current
implementation which calls dump_stack() regardless of whether register
state is available.
In preparation for making use of the generic nmi_cpu_backtrace() to
implement arch_trigger_cpumask_backtrace(), have our implementation of
show_regs() call dump_stack() and drop the explicit dump_stack() call in
arch_dump_stack() which is invoked by arch_trigger_cpumask_backtrace().
This will allow the output we produce to remain the same after a later
patch switches to using nmi_cpu_backtrace(). It may mean that we produce
extra stack output in other uses of show_regs(), but this:
1) Seems harmless.
2) Is good for consistency between arch_trigger_cpumask_backtrace()
and other users of show_regs().
3) Matches the behaviour of the ARM & PowerPC architectures.
Marked for stable back to v4.9 as a prerequisite of the following patch
"MIPS: Call dump_stack() from show_regs()".
Signed-off-by: Paul Burton <paul.burton@xxxxxxxx>
Patchwork: https://patchwork.linux-mips.org/patch/19596/
Cc: James Hogan <jhogan@xxxxxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: Huacai Chen <chenhc@xxxxxxxxxx>
Cc: linux-mips@xxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
[ Huacai: backported to 4.4: The next patch is also backported to 4.4 ]
Signed-off-by: Huacai Chen <chenhc@xxxxxxxxxx>
---
arch/mips/kernel/process.c | 4 ++--
arch/mips/kernel/traps.c | 1 +
2 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
index 1ee603d..f96048a 100644
--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -637,8 +637,8 @@ static void arch_dump_stack(void *info)
if (regs)
show_regs(regs);
-
- dump_stack();
+ else
+ dump_stack();
}
void arch_trigger_all_cpu_backtrace(bool include_self)
diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index 31ca2ed..1b90121 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -344,6 +344,7 @@ static void __show_regs(const struct pt_regs *regs)
void show_regs(struct pt_regs *regs)
{
__show_regs((struct pt_regs *)regs);
+ dump_stack();
}
void show_registers(struct pt_regs *regs)
--
2.7.0
