This patch is not correct, because the stacktrace is supposed to work around discontiguous interrupt stacks.
You should replace 'frame->fp <= fp' with 'frame->fp == fp'. Mikulas On Mon, 17 Sep 2018, Sasha Levin wrote: > From: Mikulas Patocka <[email protected]> > > [ Upstream commit 7e7df71fd57ff2894d96abb0080922bf39460a79 ] > > I've got this infinite stacktrace when debugging another problem: > [ 908.795225] INFO: rcu_preempt detected stalls on CPUs/tasks: > [ 908.796176] 1-...!: (1 GPs behind) idle=952/1/4611686018427387904 > softirq=1462/1462 fqs=355 > [ 908.797692] 2-...!: (1 GPs behind) idle=f42/1/4611686018427387904 > softirq=1550/1551 fqs=355 > [ 908.799189] (detected by 0, t=2109 jiffies, g=130, c=129, q=235) > [ 908.800284] Task dump for CPU 1: > [ 908.800871] kworker/1:1 R running task 0 32 2 > 0x00000022 > [ 908.802127] Workqueue: writecache-writeabck writecache_writeback > [dm_writecache] > [ 908.820285] Call trace: > [ 908.824785] __switch_to+0x68/0x90 > [ 908.837661] 0xfffffe00603afd90 > [ 908.844119] 0xfffffe00603afd90 > [ 908.850091] 0xfffffe00603afd90 > [ 908.854285] 0xfffffe00603afd90 > [ 908.863538] 0xfffffe00603afd90 > [ 908.865523] 0xfffffe00603afd90 > > The machine just locked up and kept on printing the same line over and > over again. This patch fixes it. > > Signed-off-by: Mikulas Patocka <[email protected]> > Signed-off-by: Will Deacon <[email protected]> > Signed-off-by: Sasha Levin <[email protected]> > --- > arch/arm64/kernel/stacktrace.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c > index d5718a060672..e160ca123da3 100644 > --- a/arch/arm64/kernel/stacktrace.c > +++ b/arch/arm64/kernel/stacktrace.c > @@ -56,6 +56,9 @@ int notrace unwind_frame(struct task_struct *tsk, struct > stackframe *frame) > frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp)); > frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8)); > > + if (frame->fp <= fp) > + return -EINVAL; > + > #ifdef CONFIG_FUNCTION_GRAPH_TRACER > if (tsk->ret_stack && > (frame->pc == (unsigned long)return_to_handler)) { > -- > 2.17.1 >
