Re: [PATCH v3 4/4] mm: prohibit NULL deference exposed for unsupported non-blockable __GFP_NOFAIL

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To: Yafang Shao <laoar.shao@xxxxxxxxx>
Subject: Re: [PATCH v3 4/4] mm: prohibit NULL deference exposed for unsupported non-blockable __GFP_NOFAIL
From: Michal Hocko <mhocko@xxxxxxxx>
Date: Mon, 19 Aug 2024 09:51:50 +0200
Cc: Barry Song <21cnbao@xxxxxxxxx>, akpm@xxxxxxxxxxxxxxxxxxxx, linux-mm@xxxxxxxxx, 42.hyeyoo@xxxxxxxxx, cl@xxxxxxxxx, hailong.liu@xxxxxxxx, hch@xxxxxxxxxxxxx, iamjoonsoo.kim@xxxxxxx, penberg@xxxxxxxxxx, rientjes@xxxxxxxxxx, roman.gushchin@xxxxxxxxx, torvalds@xxxxxxxxxxxxxxxxxxxx, urezki@xxxxxxxxx, v-songbaohua@xxxxxxxx, vbabka@xxxxxxx, virtualization@xxxxxxxxxxxxxxx, Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>, Kees Cook <kees@xxxxxxxxxx>, Eugenio Pérez <eperezma@xxxxxxxxxx>, Jason Wang <jasowang@xxxxxxxxxx>, Maxime Coquelin <maxime.coquelin@xxxxxxxxxx>, "Michael S. Tsirkin" <mst@xxxxxxxxxx>, Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
In-reply-to: <CALOAHbCcSqZx99zoAzRFHFKbRBXxLFWg=MCXR2-gL6i2bENuaw@mail.gmail.com>
References: <20240817062449.21164-1-21cnbao@gmail.com> <20240817062449.21164-5-21cnbao@gmail.com> <CALOAHbD-npQmchiRJpGvOBVOM-Li6oRyMnKAjgiHq3DasiXMUQ@mail.gmail.com> <CAGsJ_4yWPw5ihcnxxGDBVR0s69WdqZf_GQdx49u6NXEefd1pQA@mail.gmail.com> <CALOAHbBLF-Rt-RML=oOAkwW6PJDoMRTdV_6itw69xJLBrERGmQ@mail.gmail.com> <CAGsJ_4zA60pQ8qS4XzoR7ZFeAw=GmA0Xbwx18pLBR-B+nO4Mjw@mail.gmail.com> <CAGsJ_4wHCtkVau=gQRowOaJEYQ4dsSFtYx0rk13cZ+A+9gmm2g@mail.gmail.com> <CALOAHbCcSqZx99zoAzRFHFKbRBXxLFWg=MCXR2-gL6i2bENuaw@mail.gmail.com>

On Sun 18-08-24 15:07:00, Yafang Shao wrote:
> That can be avoided by a simple cond_resched() if the hard lockup or
> softlockup is the main issue ;)

No, it cannot! cond_resched from withing an atomic context is no-no. And NOWAIT
is used from withing atomic contexts.

-- 
Michal Hocko
SUSE Labs

References:
- [PATCH v3 0/4] mm: clarify nofail memory allocation
  - From: Barry Song
- [PATCH v3 4/4] mm: prohibit NULL deference exposed for unsupported non-blockable __GFP_NOFAIL
  - From: Barry Song
- Re: [PATCH v3 4/4] mm: prohibit NULL deference exposed for unsupported non-blockable __GFP_NOFAIL
  - From: Yafang Shao
- Re: [PATCH v3 4/4] mm: prohibit NULL deference exposed for unsupported non-blockable __GFP_NOFAIL
  - From: Barry Song
- Re: [PATCH v3 4/4] mm: prohibit NULL deference exposed for unsupported non-blockable __GFP_NOFAIL
  - From: Yafang Shao
- Re: [PATCH v3 4/4] mm: prohibit NULL deference exposed for unsupported non-blockable __GFP_NOFAIL
  - From: Barry Song
- Re: [PATCH v3 4/4] mm: prohibit NULL deference exposed for unsupported non-blockable __GFP_NOFAIL
  - From: Barry Song
- Re: [PATCH v3 4/4] mm: prohibit NULL deference exposed for unsupported non-blockable __GFP_NOFAIL
  - From: Yafang Shao

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