On 2022/11/16 22:15, Zqiang wrote:
> Currently, the mem_dump_obj() is invoked in call_rcu(), the
Plan to call mem_dump_obj() in rcu_do_batch().
> call_rcu() is maybe invoked in non-preemptive code segment,
> for object allocated from vmalloc(), the following scenarios
> may occur:
>
> CPU 0
> tasks context
> spin_lock(&vmap_area_lock)
> Interrupt context
> call_rcu()
> mem_dump_obj
> vmalloc_dump_obj
> spin_lock(&vmap_area_lock) <--deadlock
>
> and for PREEMPT-RT kernel, the spinlock will convert to sleepable
> lock, it also make vmap_area_lock spinlock can not acquire in
> non-preemptive code segment. therefore, this commit make the
> vmalloc_dump_obj() call in a preemptible context.
>
> Signed-off-by: Zqiang <qiang1.zhang@xxxxxxxxx>
> ---
> mm/util.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/mm/util.c b/mm/util.c
> index 12984e76767e..465f8b8824ca 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -1124,8 +1124,12 @@ void mem_dump_obj(void *object)
> return;
> }
>
> - if (vmalloc_dump_obj(object))
> - return;
> + if (is_vmalloc_addr(object)) {
> + if (preemptible() && vmalloc_dump_obj(object))
preemptible() --> !in_interrupt()?
> + return;
> + type = "vmalloc memory";
> + goto end;
> + }
Move into vmalloc_dump_obj()?
>
> if (virt_addr_valid(object))
> type = "non-slab/vmalloc memory";
> @@ -1135,7 +1139,7 @@ void mem_dump_obj(void *object)
> type = "zero-size pointer";
> else
> type = "non-paged memory";
> -
> +end:
> pr_cont(" %s\n", type);
> }
> EXPORT_SYMBOL_GPL(mem_dump_obj);
>
--
Regards,
Zhen Lei
