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Sat, 21 Dec 2019 07:36:57 -0800 (PST) Subject: Re: [PATCH 1/2] pcpu_ref: add percpu_ref_tryget_many() To: Dennis Zhou , Tejun Heo Cc: Jens Axboe , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, Christoph Lameter References: <20191218162642.GC2914998@devbig004.ftw2.facebook.com> <20191218174955.GA14991@dennisz-mbp.dhcp.thefacebook.com> From: Pavel Begunkov Autocrypt: addr=asml.silence@gmail.com; prefer-encrypt=mutual; keydata= mQINBFmKBOQBEAC76ZFxLAKpDw0bKQ8CEiYJRGn8MHTUhURL02/7n1t0HkKQx2K1fCXClbps bdwSHrhOWdW61pmfMbDYbTj6ZvGRvhoLWfGkzujB2wjNcbNTXIoOzJEGISHaPf6E2IQx1ik9 6uqVkK1OMb7qRvKH0i7HYP4WJzYbEWVyLiAxUj611mC9tgd73oqZ2pLYzGTqF2j6a/obaqha +hXuWTvpDQXqcOZJXIW43atprH03G1tQs7VwR21Q1eq6Yvy2ESLdc38EqCszBfQRMmKy+cfp W3U9Mb1w0L680pXrONcnlDBCN7/sghGeMHjGKfNANjPc+0hzz3rApPxpoE7HC1uRiwC4et83 CKnncH1l7zgeBT9Oa3qEiBlaa1ZCBqrA4dY+z5fWJYjMpwI1SNp37RtF8fKXbKQg+JuUjAa9 Y6oXeyEvDHMyJYMcinl6xCqCBAXPHnHmawkMMgjr3BBRzODmMr+CPVvnYe7BFYfoajzqzq+h EyXSl3aBf0IDPTqSUrhbmjj5OEOYgRW5p+mdYtY1cXeK8copmd+fd/eTkghok5li58AojCba jRjp7zVOLOjDlpxxiKhuFmpV4yWNh5JJaTbwCRSd04sCcDNlJj+TehTr+o1QiORzc2t+N5iJ NbILft19Izdn8U39T5oWiynqa1qCLgbuFtnYx1HlUq/HvAm+kwARAQABtDFQYXZlbCBCZWd1 bmtvdiAoc2lsZW5jZSkgPGFzbWwuc2lsZW5jZUBnbWFpbC5jb20+iQJOBBMBCAA4FiEE+6Ju PTjTbx479o3OWt5b1Glr+6UFAlmKBOQCGwMFCwkIBwIGFQgJCgsCBBYCAwECHgECF4AACgkQ Wt5b1Glr+6WxZA//QueaKHzgdnOikJ7NA/Vq8FmhRlwgtP0+E+w93kL+ZGLzS/cUCIjn2f4Q Mcutj2Neg0CcYPX3b2nJiKr5Vn0rjJ/suiaOa1h1KzyNTOmxnsqE5fmxOf6C6x+NKE18I5Jy xzLQoktbdDVA7JfB1itt6iWSNoOTVcvFyvfe5ggy6FSCcP+m1RlR58XxVLH+qlAvxxOeEr/e aQfUzrs7gqdSd9zQGEZo0jtuBiB7k98t9y0oC9Jz0PJdvaj1NZUgtXG9pEtww3LdeXP/TkFl HBSxVflzeoFaj4UAuy8+uve7ya/ECNCc8kk0VYaEjoVrzJcYdKP583iRhOLlZA6HEmn/+Gh9 4orG67HNiJlbFiW3whxGizWsrtFNLsSP1YrEReYk9j1SoUHHzsu+ZtNfKuHIhK0sU07G1OPN 2rDLlzUWR9Jc22INAkhVHOogOcc5ajMGhgWcBJMLCoi219HlX69LIDu3Y34uIg9QPZIC2jwr 24W0kxmK6avJr7+n4o8m6sOJvhlumSp5TSNhRiKvAHB1I2JB8Q1yZCIPzx+w1ALxuoWiCdwV M/azguU42R17IuBzK0S3hPjXpEi2sK/k4pEPnHVUv9Cu09HCNnd6BRfFGjo8M9kZvw360gC1 reeMdqGjwQ68o9x0R7NBRrtUOh48TDLXCANAg97wjPoy37dQE7e5Ag0EWYoE5AEQAMWS+aBV IJtCjwtfCOV98NamFpDEjBMrCAfLm7wZlmXy5I6o7nzzCxEw06P2rhzp1hIqkaab1kHySU7g dkpjmQ7Jjlrf6KdMP87mC/Hx4+zgVCkTQCKkIxNE76Ff3O9uTvkWCspSh9J0qPYyCaVta2D1 Sq5HZ8WFcap71iVO1f2/FEHKJNz/YTSOS/W7dxJdXl2eoj3gYX2UZNfoaVv8OXKaWslZlgqN jSg9wsTv1K73AnQKt4fFhscN9YFxhtgD/SQuOldE5Ws4UlJoaFX/yCoJL3ky2kC0WFngzwRF Yo6u/KON/o28yyP+alYRMBrN0Dm60FuVSIFafSqXoJTIjSZ6olbEoT0u17Rag8BxnxryMrgR dkccq272MaSS0eOC9K2rtvxzddohRFPcy/8bkX+t2iukTDz75KSTKO+chce62Xxdg62dpkZX xK+HeDCZ7gRNZvAbDETr6XI63hPKi891GeZqvqQVYR8e+V2725w+H1iv3THiB1tx4L2bXZDI DtMKQ5D2RvCHNdPNcZeldEoJwKoA60yg6tuUquvsLvfCwtrmVI2rL2djYxRfGNmFMrUDN1Xq F3xozA91q3iZd9OYi9G+M/OA01husBdcIzj1hu0aL+MGg4Gqk6XwjoSxVd4YT41kTU7Kk+/I 5/Nf+i88ULt6HanBYcY/+Daeo/XFABEBAAGJAjYEGAEIACAWIQT7om49ONNvHjv2jc5a3lvU aWv7pQUCWYoE5AIbDAAKCRBa3lvUaWv7pfmcEACKTRQ28b1y5ztKuLdLr79+T+LwZKHjX++P 4wKjEOECCcB6KCv3hP+J2GCXDOPZvdg/ZYZafqP68Yy8AZqkfa4qPYHmIdpODtRzZSL48kM8 LRzV8Rl7J3ItvzdBRxf4T/Zseu5U6ELiQdCUkPGsJcPIJkgPjO2ROG/ZtYa9DvnShNWPlp+R uPwPccEQPWO/NP4fJl2zwC6byjljZhW5kxYswGMLBwb5cDUZAisIukyAa8Xshdan6C2RZcNs rB3L7vsg/R8UCehxOH0C+NypG2GqjVejNZsc7bgV49EOVltS+GmGyY+moIzxsuLmT93rqyII 5rSbbcTLe6KBYcs24XEoo49Zm9oDA3jYvNpeYD8rDcnNbuZh9kTgBwFN41JHOPv0W2FEEWqe JsCwQdcOQ56rtezdCJUYmRAt3BsfjN3Jn3N6rpodi4Dkdli8HylM5iq4ooeb5VkQ7UZxbCWt UVMKkOCdFhutRmYp0mbv2e87IK4erwNHQRkHUkzbsuym8RVpAZbLzLPIYK/J3RTErL6Z99N2 m3J6pjwSJY/zNwuFPs9zGEnRO4g0BUbwGdbuvDzaq6/3OJLKohr5eLXNU3JkT+3HezydWm3W OPhauth7W0db74Qd49HXK0xe/aPrK+Cp+kU1HRactyNtF8jZQbhMCC8vMGukZtWaAwpjWiiH bA== Message-ID: Date: Sat, 21 Dec 2019 18:36:32 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: <20191218174955.GA14991@dennisz-mbp.dhcp.thefacebook.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="3o66J1ZwYzbZnzQJ7MM5XEiLrkSizyNNG" Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --3o66J1ZwYzbZnzQJ7MM5XEiLrkSizyNNG Content-Type: multipart/mixed; boundary="Jx8zujedjt6X5jhErYw1sz4LbnBZNdXBa"; protected-headers="v1" From: Pavel Begunkov To: Dennis Zhou , Tejun Heo Cc: Jens Axboe , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, Christoph Lameter Message-ID: Subject: Re: [PATCH 1/2] pcpu_ref: add percpu_ref_tryget_many() References: <20191218162642.GC2914998@devbig004.ftw2.facebook.com> <20191218174955.GA14991@dennisz-mbp.dhcp.thefacebook.com> In-Reply-To: <20191218174955.GA14991@dennisz-mbp.dhcp.thefacebook.com> --Jx8zujedjt6X5jhErYw1sz4LbnBZNdXBa Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 18/12/2019 20:49, Dennis Zhou wrote: > On Wed, Dec 18, 2019 at 08:26:42AM -0800, Tejun Heo wrote: >> (cc'ing Dennis and Christoph and quoting whole body) >> >> Pavel, can you please cc percpu maintainers on related changes? My bad, lost cc's in the way. >> >> The patch looks fine to me. Please feel free to add my acked-by. >> >> On Tue, Dec 17, 2019 at 04:42:59PM -0700, Jens Axboe wrote: >>> CC Tejun on this one. Looks fine to me, and matches the put path. Thanks both for taking a look! >>> >>> >>> On 12/17/19 3:28 PM, Pavel Begunkov wrote: >>>> Add percpu_ref_tryget_many(), which works the same way as >>>> percpu_ref_tryget(), but grabs specified number of refs. >>>> >>>> Signed-off-by: Pavel Begunkov >>>> --- >>>> include/linux/percpu-refcount.h | 24 ++++++++++++++++++++---- >>>> 1 file changed, 20 insertions(+), 4 deletions(-) >>>> >>>> diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-= refcount.h >>>> index 390031e816dc..19079b62ce31 100644 >>>> --- a/include/linux/percpu-refcount.h >>>> +++ b/include/linux/percpu-refcount.h >>>> @@ -210,15 +210,17 @@ static inline void percpu_ref_get(struct percp= u_ref *ref) >>>> } >>>> =20 >>>> /** >>>> - * percpu_ref_tryget - try to increment a percpu refcount >>>> + * percpu_ref_tryget_many - try to increment a percpu refcount >>>> * @ref: percpu_ref to try-get >>>> + * @nr: number of references to get >>>> * >>>> * Increment a percpu refcount unless its count already reached zer= o. >>>> * Returns %true on success; %false on failure. >=20 > Minor nit: would be nice to change this so the two don't have identical= > comments. (eg: Increment a percpu refcount by @nr unless...) >>>> * >>>> * This function is safe to call as long as @ref is between init an= d exit. >>>> */ >>>> -static inline bool percpu_ref_tryget(struct percpu_ref *ref) >>>> +static inline bool percpu_ref_tryget_many(struct percpu_ref *ref, >>>> + unsigned long nr) >>>> { >>>> unsigned long __percpu *percpu_count; >>>> bool ret; >>>> @@ -226,10 +228,10 @@ static inline bool percpu_ref_tryget(struct pe= rcpu_ref *ref) >>>> rcu_read_lock(); >>>> =20 >>>> if (__ref_is_percpu(ref, &percpu_count)) { >>>> - this_cpu_inc(*percpu_count); >>>> + this_cpu_add(*percpu_count, nr); >>>> ret =3D true; >>>> } else { >>>> - ret =3D atomic_long_inc_not_zero(&ref->count); >>>> + ret =3D atomic_long_add_unless(&ref->count, nr, 0); >>>> } >>>> =20 >>>> rcu_read_unlock(); >>>> @@ -237,6 +239,20 @@ static inline bool percpu_ref_tryget(struct per= cpu_ref *ref) >>>> return ret; >>>> } >>>> =20 >>>> +/** >>>> + * percpu_ref_tryget - try to increment a percpu refcount >>>> + * @ref: percpu_ref to try-get >>>> + * >>>> + * Increment a percpu refcount unless its count already reached zer= o. >>>> + * Returns %true on success; %false on failure. >>>> + * >>>> + * This function is safe to call as long as @ref is between init an= d exit. >>>> + */ >>>> +static inline bool percpu_ref_tryget(struct percpu_ref *ref) >>>> +{ >>>> + return percpu_ref_tryget_many(ref, 1); >>>> +} >>>> + >>>> /** >>>> * percpu_ref_tryget_live - try to increment a live percpu refcount= >>>> * @ref: percpu_ref to try-get >>>> >>> >>> >>> --=20 >>> Jens Axboe >>> >> >> --=20 >> tejun >=20 > Acked-by: Dennis Zhou >=20 > Thanks, > Dennis >=20 --=20 Pavel Begunkov --Jx8zujedjt6X5jhErYw1sz4LbnBZNdXBa-- --3o66J1ZwYzbZnzQJ7MM5XEiLrkSizyNNG Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEE+6JuPTjTbx479o3OWt5b1Glr+6UFAl3+PAAACgkQWt5b1Glr +6Xjog//X7kw1OUa2qr1kVtmvkQFCER2aJ3gmT7aYGI4gnTJQvDFryefpqi9Vvoa UCt9uahVMMaeaSeIvOY6Ol9iwVNVwTqj9hFr3ZTpVW+3MfdPR5LNQUf1RCd2Oyqq 0d09jnChLfUGFhiSPBQLKAYkxGTxFGjworgpONe3nrwDKg7foPvpNMjnP79DIpZ5 JpwHiachIEi2tDpjtgD4ZbBkLMydE4rQWfFg1/7QAUAPFlGmN7KqhYaNaLumj74r CJk5B2IzlTmjJE4CxGJl0la23TdCRd1yFRda5hRfXkVmvPgQtIkLbgcJAhADx9h1 FPvWS8AZbZLYmxOm0eWi38Rw/KcY234gL8vTgy7215i/oE8WrVlSbgfZBioL3wgM VJrhZZcFHQ4EbrR2lt5//lF5Zy/2WO2sTZZeib0SgOSn7xt5a3WnK+NzcorRiqL6 wEIq3UN4/drz7pV80v0akG09uVXU5xxZTU5L2LeDJiwRYtO94dURSkkZYxvxkXv2 pjOUiPLlm47b2ZecLzpJdhPxLoWCQLtsJl3H+HeniL0r78a9Yrzj0ku/Ye4yp8YI VgzZuGX6s/B+vZ7mSC7jMek2M3ud4dS3O5vuq3cjnlxy68N3V8w4PWgt9S33qs3F xSuZPw+17ECq1fdtz9oex1/0J/9VekYa+RG4cFtI9SoNMe8+YJg= =RMCN -----END PGP SIGNATURE----- --3o66J1ZwYzbZnzQJ7MM5XEiLrkSizyNNG--