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[2003:d9:970a:ab00:ae94:992d:1079:bfc]) by smtp.googlemail.com with ESMTPSA id i1sm7601297wml.26.2021.12.23.03.52.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 23 Dec 2021 03:52:18 -0800 (PST) Message-ID: <937f1320-6b7e-9aa2-2a21-7fd2f94eeb32@colorfullife.com> Date: Thu, 23 Dec 2021 12:52:17 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.4.0 Subject: Re: [PATCH] mm/util.c: Make kvfree() safe for calling while holding spinlocks Content-Language: en-US To: Vasily Averin , LKML , Andrew Morton Cc: cgel.zte@gmail.com, shakeelb@google.com, rdunlap@infradead.org, dbueso@suse.de, unixbhaskar@gmail.com, chi.minghao@zte.com.cn, arnd@arndb.de, Zeal Robot , linux-mm@kvack.org, 1vier1@web.de, stable@vger.kernel.org References: <20211222194828.15320-1-manfred@colorfullife.com> <3ca4dec8-f0bd-740f-73c8-34fc6fc1cf66@virtuozzo.com> From: Manfred Spraul In-Reply-To: <3ca4dec8-f0bd-740f-73c8-34fc6fc1cf66@virtuozzo.com> Content-Type: text/plain; charset=UTF-8; format=flowed Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=colorfullife-com.20210112.gappssmtp.com header.s=20210112 header.b=SQOpFeLu; dmarc=none; spf=pass (imf17.hostedemail.com: domain of manfred@colorfullife.com designates 209.85.128.44 as permitted sender) smtp.mailfrom=manfred@colorfullife.com X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 4687A40002 X-Stat-Signature: pbxzqr73czsa6shptbbfphu3jcjtieho X-HE-Tag: 1640260338-626200 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hello Vasily, On 12/23/21 08:21, Vasily Averin wrote: > > I would prefer to release memory ASAP if it's possible. > What do you think about this change? > --- a/mm/util.c > +++ b/mm/util.c > @@ -614,9 +614,12 @@ EXPORT_SYMBOL(kvmalloc_node); > */ > void kvfree(const void *addr) > { > - if (is_vmalloc_addr(addr)) > - vfree(addr); > - else > + if (is_vmalloc_addr(addr)) { > + if (in_atomic()) > + vfree_atomic(); > + else > + vfree(addr); > + } else > kfree(addr); > } > EXPORT_SYMBOL(kvfree); > Unfortunately this cannot work: > /* > * Are we running in atomic context? =C2=A0WARNING: this macro cannot > * always detect atomic context; in particular, it cannot know about > * held spinlocks in non-preemptible kernels. =C2=A0Thus it should not b= e > * used in the general case to determine whether sleeping is possible. > * Do not use in_atomic() in driver code. > */ > #define in_atomic() =C2=A0=C2=A0=C2=A0=C2=A0(preempt_count() !=3D 0) > -- =C2=A0=C2=A0=C2=A0 Manfred