On Sunday, October 16, 2016 11:56 PM Vegard Nossum wrote:
>
> If something we call in the fail_dump() code path tries to acquire a
> resource that might fail (due to fault injection), then we should not
> try to recurse back into the fault injection code.
>
> I've seen this happen with the console semaphore in the upcoming
> semaphore trylock fault injection code.
>
> Cc: Hillf Danton <hillf...@alibaba-inc.com>
> Signed-off-by: Vegard Nossum <vegard.nos...@oracle.com>
> ---
> lib/fault-inject.c | 34 ++++++++++++++++++++++++++++------
> 1 file changed, 28 insertions(+), 6 deletions(-)
>
> diff --git a/lib/fault-inject.c b/lib/fault-inject.c
> index 6a823a5..adba7c9 100644
> --- a/lib/fault-inject.c
> +++ b/lib/fault-inject.c
> @@ -100,6 +100,33 @@ static inline bool fail_stacktrace(struct fault_attr
> *attr)
>
> #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
>
> +static DEFINE_PER_CPU(int, fault_active);
> +
> +static bool __fail(struct fault_attr *attr)
> +{
> + bool ret = false;
> +
> + /*
> + * Prevent recursive fault injection (this could happen if for
> + * example printing the fault would itself run some code that
> + * could fail)
> + */
> + preempt_disable();
> + if (unlikely(__this_cpu_inc_return(fault_active) != 1))
> + goto out;
> +
> + ret = true;
> + fail_dump(attr);
> +
> + if (atomic_read(&attr->times) != -1)
> + atomic_dec_not_zero(&attr->times);
> +
> +out:
> + __this_cpu_dec(fault_active);
> + preempt_enable();
Given no see other patches in this set, I could easily miss
anything important and correct me please.
Though added, there are no words in the change log about
preempt, and my wonder again is: can we add it in contexts
like the fast path of buddy allocator?
thanks
Hillf
> + return ret;
> +}
> +
> /*
> * This code is stolen from failmalloc-1.0
> * http://www.nongnu.org/failmalloc/
> @@ -134,12 +161,7 @@ bool should_fail(struct fault_attr *attr, ssize_t size)
> if (!fail_stacktrace(attr))
> return false;
>
> - fail_dump(attr);
> -
> - if (atomic_read(&attr->times) != -1)
> - atomic_dec_not_zero(&attr->times);
> -
> - return true;
> + return __fail(attr);
> }
> EXPORT_SYMBOL_GPL(should_fail);
>
> --
> 2.10.0.479.g221bd91
