Date: Thu, 30 Aug 2012 12:01:17 +0400 From: Sergey Kandaurov <pluknet@gmail.com> To: Vijay Singh <vijju.singh@gmail.com> Cc: net@freebsd.org Subject: Re: sorele() and ACCEPT_LOCK() Message-ID: <CAE-mSO%2B3r-4E034okkuNYiYtcaaQtFFgD0iAtTjLyYteaUOBjw@mail.gmail.com> In-Reply-To: <CALCNsJTQNkPv41M0vBMoQJpFFLFHw7Q4Pf__rOmO%2BXADxAGi4g@mail.gmail.com> References: <CALCNsJTQNkPv41M0vBMoQJpFFLFHw7Q4Pf__rOmO%2BXADxAGi4g@mail.gmail.com>
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On 30 August 2012 04:23, Vijay Singh <vijju.singh@gmail.com> wrote:
> Is there any reason why sorele() needs the accept lock to be held?
>
> 231 #define sorele(so) do { \
> 232 ACCEPT_LOCK_ASSERT(); \
> 233 SOCK_LOCK_ASSERT(so); \
> 234 if ((so)->so_count <= 0) \
> 235 panic("sorele"); \
> 236 if (--(so)->so_count == 0) \
> 237 sofree(so); \
> 238 else { \
> 239 SOCK_UNLOCK(so); \
> 240 ACCEPT_UNLOCK(); \
> 241 } \
> 242 } while (0)
sofree() needs accept lock to be held to operate on a qstate field.
sofree() callers cannot be changed to push accept lock acquisition into
sofree() because that would require to reacquire sock lock around accept
lock to take locks in order; this in turn opens race.
See r136682 for details.
--
wbr,
pluknet
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