From: Linus Torvalds <torvalds@linux-foundation.org>
To: Jason Wessel <jason.wessel@windriver.com>
Cc: Will Deacon <will.deacon@arm.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
kgdb-bugreport@lists.sourceforge.net, linux-arm@vger.kernel.org,
Russell King - ARM Linux <linux@arm.linux.org.uk>
Subject: Re: [PATCH 4/5] kgdb: Use atomic operators which use barriers
Date: Fri, 2 Apr 2010 12:46:14 -0700 (PDT) [thread overview]
Message-ID: <alpine.LFD.2.00.1004021244140.3634@i5.linux-foundation.org> (raw)
In-Reply-To: <alpine.LFD.2.00.1004021238270.3634@i5.linux-foundation.org>
On Fri, 2 Apr 2010, Linus Torvalds wrote:
>
> All that matters is that the above kind of while loop must work. The
> architecture needs to do whatever it needs to do to make it work. End of
> discussion. If on ARM6 that means "smp_mb()", then that's an ARM6
> implementation issue.
Put another way: from a kernel standpoint, cpu_relax() in _no_ way implies
a memory barrier. That has always been true, and that continues to be
true.
But Linux does expect that if some other CPU modifies a memory location,
then we _will_ see that modification eventually. If the CPU needs help to
do so, then cpu_relax() needs to do that. Again - this has nothing to do
with memory barriers. It's just a basic requirement.
Linus
next prev parent reply other threads:[~2010-04-02 19:50 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-02 18:32 [GIT PULL] kgdb fixes for 2.6.34-rc3 Jason Wessel
2010-04-02 18:32 ` [PATCH 1/5] kgdb: have ebin2mem call probe_kernel_write once Jason Wessel
2010-04-02 18:32 ` [PATCH 2/5] kgdbts,sh: Add in breakpoint pc offset for superh Jason Wessel
2010-04-02 18:32 ` [PATCH 3/5] kgdb: eliminate kgdb_wait(), all cpus enter the same way Jason Wessel
2010-04-02 18:32 ` [PATCH 4/5] kgdb: Use atomic operators which use barriers Jason Wessel
2010-04-02 18:32 ` [PATCH 5/5] kgdb: Turn off tracing while in the debugger Jason Wessel
2010-04-02 19:12 ` [PATCH 4/5] kgdb: Use atomic operators which use barriers Linus Torvalds
2010-04-02 19:37 ` Jason Wessel
2010-04-02 19:43 ` Linus Torvalds
2010-04-02 19:46 ` Linus Torvalds [this message]
2010-04-02 20:07 ` Linus Torvalds
2010-04-02 22:25 ` Russell King - ARM Linux
2010-04-02 23:24 ` Linus Torvalds
2010-04-03 16:08 ` Russell King - ARM Linux
2010-04-05 9:21 ` Pavel Machek
2010-04-05 14:56 ` Linus Torvalds
2010-04-02 19:47 ` [Kgdb-bugreport] [PATCH 4/5] kgdb: Use atomic operators whichuse barriers Jason Wessel
2010-04-02 19:47 ` Linus Torvalds
2010-04-02 20:00 ` Jason Wessel
2010-04-08 16:27 ` Dmitry Adamushko
2010-04-19 15:21 ` Will Deacon
[not found] ` <000501cad70a$26ca7e10$745f7a30$@deacon@arm.com>
2010-04-08 14:55 ` [PATCH 4/5] kgdb: Use atomic operators which use barriers Linus Torvalds
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