Re: [PATCH V5] x86 spinlock: Fix memory corruption on completing completions

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 02/15/2015 09:47 PM, Oleg Nesterov wrote:
Well, I regret I mentioned the lack of barrier after enter_slowpath ;)

On 02/15, Raghavendra K T wrote:

@@ -46,7 +46,8 @@ static __always_inline bool static_key_false(struct static_key *key);

  static inline void __ticket_enter_slowpath(arch_spinlock_t *lock)
  {
-	set_bit(0, (volatile unsigned long *)&lock->tickets.tail);
+	set_bit(0, (volatile unsigned long *)&lock->tickets.head);
+	barrier();
  }

Because this barrier() looks really confusing.

Firsty, it is equally unneeded on x86. At the same time, it can not help.
We need a memory barrier() between set_bit(SLOWPATH) and READ_ONCE(head)
to avoid the race with spin_unlock().

So I think you should replace it with smp_mb__after_atomic() or remove it.


I resent the patch the above change.


Other than that I believe this version is correct. So I won't insist, this
is cosmetic after all.

Thanks Oleg.

_______________________________________________
Virtualization mailing list
Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
https://lists.linuxfoundation.org/mailman/listinfo/virtualization




[Index of Archives]     [KVM Development]     [Libvirt Development]     [Libvirt Users]     [CentOS Virtualization]     [Netdev]     [Ethernet Bridging]     [Linux Wireless]     [Kernel Newbies]     [Security]     [Linux for Hams]     [Netfilter]     [Bugtraq]     [Yosemite Forum]     [MIPS Linux]     [ARM Linux]     [Linux RAID]     [Linux Admin]     [Samba]

  Powered by Linux