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    Subject[PATCH AUTOSEL 4.18 032/136] arm64: fix infinite stacktrace
    Date
    From: Mikulas Patocka <mpatocka@redhat.com>

    [ 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 <mpatocka@redhat.com>
    Signed-off-by: Will Deacon <will.deacon@arm.com>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    ---
    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
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