From: Eric Dumazet <eric.dumazet@gmail•com>
To: Jiri Olsa <jolsa@redhat•com>
Cc: netdev@vger•kernel.org, linux-kernel@vger•kernel.org,
fbl@redhat•com, nhorman@redhat•com, davem@redhat•com,
htejun@gmail•com, jarkao2@gmail•com, oleg@redhat•com,
davidel@xmailserver•org, eric.dumazet@gmail•com
Subject: Re: [PATCHv2 2/2] memory barrier: adding smp_mb__after_lock
Date: Tue, 30 Jun 2009 13:14:20 +0200 [thread overview]
Message-ID: <4A49F38C.80104@gmail.com> (raw)
In-Reply-To: <20090630104106.GD9657@jolsa.lab.eng.brq.redhat.com>
Jiri Olsa a écrit :
> Adding smp_mb__after_lock define to be used as a smp_mb call after
> a lock.
>
> Making it nop for x86, since {read|write|spin}_lock() on x86 are
> full memory barriers.
>
> wbr,
> jirka
>
>
> Signed-off-by: Jiri Olsa <jolsa@redhat•com>
>
> ---
> arch/x86/include/asm/spinlock.h | 3 +++
> include/linux/spinlock.h | 5 +++++
> include/net/sock.h | 2 +-
> 3 files changed, 9 insertions(+), 1 deletions(-)
>
> diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h
> index b7e5db8..39ecc5f 100644
> --- a/arch/x86/include/asm/spinlock.h
> +++ b/arch/x86/include/asm/spinlock.h
> @@ -302,4 +302,7 @@ static inline void __raw_write_unlock(raw_rwlock_t *rw)
> #define _raw_read_relax(lock) cpu_relax()
> #define _raw_write_relax(lock) cpu_relax()
>
> +/* The {read|write|spin}_lock() on x86 are full memory barriers. */
> +#define smp_mb__after_lock() do { } while (0)
> +
> #endif /* _ASM_X86_SPINLOCK_H */
> diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h
> index 252b245..ae053bd 100644
> --- a/include/linux/spinlock.h
> +++ b/include/linux/spinlock.h
> @@ -132,6 +132,11 @@ do { \
> #endif /*__raw_spin_is_contended*/
> #endif
>
> +/* The lock does not imply full memory barrier. */
> +#ifndef smp_mb__after_lock
> +#define smp_mb__after_lock() smp_mb()
> +#endif
> +
> /**
> * spin_unlock_wait - wait until the spinlock gets unlocked
> * @lock: the spinlock in question.
> diff --git a/include/net/sock.h b/include/net/sock.h
> index a12df10..0d57e83 100644
> --- a/include/net/sock.h
> +++ b/include/net/sock.h
> @@ -1277,7 +1277,7 @@ static inline void sock_poll_wait(struct file *filp,
> *
> * This memory barrier is paired in the sk_has_sleeper.
> */
> - smp_mb();
> + smp_mb__after_lock();
> }
> }
I believe you took wrong point to use this new thing :)
It was meant to be used in sk_has_sleeper() only (as sk_has_sleeper()
follows a read_lock())
next prev parent reply other threads:[~2009-06-30 11:14 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-06-30 10:36 [PATCHv2 0/2] net: fix race in the receive/select Jiri Olsa
2009-06-30 10:39 ` [PATCHv2 1/2] net: adding memory barrier to the poll and receive callbacks Jiri Olsa
2009-06-30 10:41 ` [PATCHv2 2/2] memory barrier: adding smp_mb__after_lock Jiri Olsa
2009-06-30 11:14 ` Eric Dumazet [this message]
2009-06-30 12:13 ` Jiri Olsa
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4A49F38C.80104@gmail.com \
--to=eric.dumazet@gmail$(echo .)com \
--cc=davem@redhat$(echo .)com \
--cc=davidel@xmailserver$(echo .)org \
--cc=fbl@redhat$(echo .)com \
--cc=htejun@gmail$(echo .)com \
--cc=jarkao2@gmail$(echo .)com \
--cc=jolsa@redhat$(echo .)com \
--cc=linux-kernel@vger$(echo .)kernel.org \
--cc=netdev@vger$(echo .)kernel.org \
--cc=nhorman@redhat$(echo .)com \
--cc=oleg@redhat$(echo .)com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox