From: Li Zhong <zhong@linux.vnet.ibm.com>
To: PowerPC email list <linuxppc-dev@lists.ozlabs.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>,
shreyas@linux.vnet.ibm.com, ego@linux.vnet.ibm.com
Subject: [RFC PATCH] powerpc/powernv: recheck lock bit in core_idle_lock_held after lwarx
Date: Tue, 25 Oct 2016 11:24:34 +0800 [thread overview]
Message-ID: <1477365874.10026.7.camel@TP420> (raw)
The core_idle_lock_held loops when the lock bit is held by others.
However, it is possible that after the lock bit is cleared, some one
else sees it first and sets the lock bit. And lwarx loads a value with
lock bit set, and the lock bit may be cleared in the following stwcx.
It is possible the first one is still executing in the critical section.
This patch rechecks the lock bit after lwarx, and go back to loop if it
is set.
Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
---
arch/powerpc/kernel/idle_book3s.S | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S
index bd739fe..ce07b3f 100644
--- a/arch/powerpc/kernel/idle_book3s.S
+++ b/arch/powerpc/kernel/idle_book3s.S
@@ -99,6 +99,8 @@ core_idle_lock_held:
bne 3b
HMT_MEDIUM
lwarx r15,0,r14
+ andi. r9,r15,PNV_CORE_IDLE_LOCK_BIT
+ bne- core_idle_lock_held
blr
/*
--
1.9.1
next reply other threads:[~2016-10-25 3:24 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-25 3:24 Li Zhong [this message]
2016-10-25 4:15 ` [RFC PATCH] powerpc/powernv: recheck lock bit in core_idle_lock_held after lwarx Paul Mackerras
2016-10-25 5:09 ` Li Zhong
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