Subject: Re: 34-rc1-git3 build failure with CGROUP_MEM_RES_CTLR_SWAP=y

From: Michael Ellerman <[email-masked]>
Date: Mon, 15 Mar 2010 12:04:13 +1100

On Sun, 2010-03-14 at 16:18 +0530, Sachin Sant wrote:
> On a PowerPC box, latest 34-rc1 git(d89b218b8...) fails to build
> with CGROUPS_MEM_RES_CTRL_SWAP=y. 
> 
> LD      init/built-in.o
> LD      .tmp_vmlinux1
> mm/built-in.o: In function __xchg:
> arch/powerpc/include/asm/system.h:331: undefined reference to .__xchg_called_with_bad_pointer
> mm/built-in.o: In function __cmpxchg:
> arch/powerpc/include/asm/system.h:474: undefined reference to .__cmpxchg_called_with_bad_pointer
> make: *** [.tmp_vmlinux1] Error 1
> 
> The code in question was added via commit 024914477e...
> 
> memcg: move charges of anonymous swap

struct swap_cgroup
{                                                        
	unsigned short          id;
};

+unsigned short swap_cgroup_cmpxchg(swp_entry_t ent,
+                                       unsigned short old, unsigned short new)
+{
...
+       struct swap_cgroup *sc;
...
+       if (cmpxchg(&sc->id, old, new) == old)

On powerpc cmpxchg() currently only handles u32 & u64.

cheers