Re: [Kgdb-bugreport] [PATCH 4/5] kgdb: Use atomic operators whichusebarriers

From: Jason Wessel
Date: Fri Apr 02 2010 - 16:01:08 EST

On 04/02/2010 02:47 PM, Linus Torvalds wrote:
>> From: Jason Wessel <jason.wessel@xxxxxxxxxxxxx>
>> Subject: [PATCH] kgdb: Use atomic operators which use barriers
>> The cpu_relax() does not mandate that there is an smp memory barrier.
>> As a result on the arm smp architecture the kernel debugger can hang
>> on entry from time to time, as shown by the kgdb regression tests.
> Now your changelog makes no sense any more.

It is revised now and pushed. Regression testing on the HW I have has
passed as well now.

For the series the pull looks like:

drivers/misc/kgdbts.c | 6 ++
kernel/kgdb.c | 205
2 files changed, 109 insertions(+), 102 deletions(-)


From: Jason Wessel <jason.wessel@xxxxxxxxxxxxx>
Subject: [PATCH] kgdb: use atomic_inc and atomic_dec instead of atomic_set

Memory barriers should be used for the kgdb cpu synchronization. The
atomic_set() does not imply a memory barrier.

Reported-by: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Jason Wessel <jason.wessel@xxxxxxxxxxxxx>
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