On Wed 16-09-15 19:59:59, Yaowei Bai wrote:
> Introduce is_sysrq_oom helper function indicating oom kill triggered
> by sysrq to improve readability.
> 
> No functional changes.

I was complaining about a subtle semantic of order -1 when it was
introduced. This is easier to follow. At least for me.
 
> Signed-off-by: Yaowei Bai <[email protected]>

Acked-by: Michal Hocko <[email protected]>

> ---
>  mm/oom_kill.c | 17 +++++++++++++----
>  1 file changed, 13 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index 1ecc0bc..7b6228e 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -118,6 +118,15 @@ found:
>       return t;
>  }
>  
> +/*
> + * order == -1 means the oom kill is required by sysrq, otherwise only
> + * for display purposes.
> + */
> +static inline bool is_sysrq_oom(struct oom_control *oc)
> +{
> +     return oc->order == -1;
> +}
> +
>  /* return true if the task is not adequate as candidate victim task. */
>  static bool oom_unkillable_task(struct task_struct *p,
>               struct mem_cgroup *memcg, const nodemask_t *nodemask)
> @@ -265,7 +274,7 @@ enum oom_scan_t oom_scan_process_thread(struct 
> oom_control *oc,
>        * Don't allow any other task to have access to the reserves.
>        */
>       if (test_tsk_thread_flag(task, TIF_MEMDIE)) {
> -             if (oc->order != -1)
> +             if (!is_sysrq_oom(oc))
>                       return OOM_SCAN_ABORT;
>       }
>       if (!task->mm)
> @@ -278,7 +287,7 @@ enum oom_scan_t oom_scan_process_thread(struct 
> oom_control *oc,
>       if (oom_task_origin(task))
>               return OOM_SCAN_SELECT;
>  
> -     if (task_will_free_mem(task) && oc->order != -1)
> +     if (task_will_free_mem(task) && !is_sysrq_oom(oc))
>               return OOM_SCAN_ABORT;
>  
>       return OOM_SCAN_OK;
> @@ -608,7 +617,7 @@ void check_panic_on_oom(struct oom_control *oc, enum 
> oom_constraint constraint,
>                       return;
>       }
>       /* Do not panic for oom kills triggered by sysrq */
> -     if (oc->order == -1)
> +     if (is_sysrq_oom(oc))
>               return;
>       dump_header(oc, NULL, memcg);
>       panic("Out of memory: %s panic_on_oom is enabled\n",
> @@ -688,7 +697,7 @@ bool out_of_memory(struct oom_control *oc)
>  
>       p = select_bad_process(oc, &points, totalpages);
>       /* Found nothing?!?! Either we hang forever, or we panic. */
> -     if (!p && oc->order != -1) {
> +     if (!p && !is_sysrq_oom(oc)) {
>               dump_header(oc, NULL, NULL);
>               panic("Out of memory and no killable processes...\n");
>       }
> -- 
> 1.9.1
> 
> 
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-- 
Michal Hocko
SUSE Labs
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