Hi!
On 11/02/16 21:53, Yang Shi wrote:
Switching between stacks is only valid if we are tracing ourselves while on the irq_stack, so it is only valid when in current and non-preemptible context, otherwise is is just zeroed off.
Given it was picked up with CONFIG_DEBUG_PREEMPT:
Fixes: 132cd887b5c5 ("arm64: Modify stack trace and dump for use with irq_stack")
Signed-off-by: Yang Shi yang.shi@linaro.org
arch/arm64/kernel/stacktrace.c | 13 ++++++------- arch/arm64/kernel/traps.c | 11 ++++++++++- 2 files changed, 16 insertions(+), 8 deletions(-)
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index 12a18cb..d9751a4 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -44,14 +44,13 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame) unsigned long irq_stack_ptr; /*
* Use raw_smp_processor_id() to avoid false-positives from* CONFIG_DEBUG_PREEMPT. get_wchan() calls unwind_frame() on sleeping* task stacks, we can be pre-empted in this case, so* {raw_,}smp_processor_id() may give us the wrong value. Sleeping* tasks can't ever be on an interrupt stack, so regardless of cpu,* the checks will always fail.
* Switching between stacks is valid when tracing current and in* non-preemptible context.
- irq_stack_ptr = IRQ_STACK_PTR(raw_smp_processor_id());
- if (tsk == current && !preemptible())
irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());- else
irq_stack_ptr = 0;low = frame->sp; /* irq stacks are not THREAD_SIZE aligned */ diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index cbedd72..7d8db3a 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -146,9 +146,18 @@ static void dump_instr(const char *lvl, struct pt_regs *regs) static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk) { struct stackframe frame;
- unsigned long irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
- unsigned long irq_stack_ptr; int skip;
- /*
* Switching between stacks is valid when tracing current and in
Nit: Two spaces: "between[ ][ ]stacks"
* non-preemptible context.*/- if (tsk == current && !preemptible())
irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());- else
irq_stack_ptr = 0;- pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
if (!tsk)
Neither file includes 'linux/preempt.h' for the definition of preemptible(). (I can't talk: I should have included smp.h for smp_processor_id())
Acked-by: James Morse james.morse@arm.com Tested-by: James Morse james.morse@arm.com
Thanks!
James