gcc-4.6.0 generates no code for sub_preempt_count()

gcc-4.6.0 generates no code for sub_preempt_count()

[Richard Weinberger]

Hi,

I'm facing a very strange issue with gcc-4.6.0 and UML.
Within __local_bh_enable() gcc generates no code for sub_preempt_count().

See:
http://userweb.kernel.org/~rw/uml-gcc460/__local_bh_enable-gcc460.txt
vs.
http://userweb.kernel.org/~rw/uml-gcc460/__local_bh_enable-gcc431.txt

Interestingly it generates code for add_preempt_count().
I can reproduce this on x86 and x86_64.

The problem has to do with UML's current_thread_info() function.
When I replace it with arch/x86's (unportable) variant gcc generates code.

Any ideas whether this is a gcc or a kernel issue?
Thanks,
//richard

Re: gcc-4.6.0 generates no code for sub_preempt_count()

[Mikael Pettersson]

Richard Weinberger writes:
 > Hi,
 > 
 > I'm facing a very strange issue with gcc-4.6.0 and UML.
 > Within __local_bh_enable() gcc generates no code for sub_preempt_count().
 > 
 > See:
 > http://userweb.kernel.org/~rw/uml-gcc460/__local_bh_enable-gcc460.txt
 > vs.
 > http://userweb.kernel.org/~rw/uml-gcc460/__local_bh_enable-gcc431.txt
 > 
 > Interestingly it generates code for add_preempt_count().
 > I can reproduce this on x86 and x86_64.
 > 
 > The problem has to do with UML's current_thread_info() function.
 > When I replace it with arch/x86's (unportable) variant gcc generates code.
 > 
 > Any ideas whether this is a gcc or a kernel issue?

Please provide a standalone test case.

Re: gcc-4.6.0 generates no code for sub_preempt_count()

[Richard Weinberger]

Am Donnerstag 14 April 2011, 09:49:14 schrieb Mikael Pettersson:
> Richard Weinberger writes:
>  > Hi,
>  > 
>  > I'm facing a very strange issue with gcc-4.6.0 and UML.
>  > Within __local_bh_enable() gcc generates no code for
>  > sub_preempt_count().
>  > 
>  > See:
>  > http://userweb.kernel.org/~rw/uml-gcc460/__local_bh_enable-gcc460.txt
>  > vs.
>  > http://userweb.kernel.org/~rw/uml-gcc460/__local_bh_enable-gcc431.txt
>  > 
>  > Interestingly it generates code for add_preempt_count().
>  > I can reproduce this on x86 and x86_64.
>  > 
>  > The problem has to do with UML's current_thread_info() function.
>  > When I replace it with arch/x86's (unportable) variant gcc generates
>  > code.
>  > 
>  > Any ideas whether this is a gcc or a kernel issue?
> 
> Please provide a standalone test case.

There you go!
http://userweb.kernel.org/~rw/uml-gcc460/testcase.c

Thanks,
//richard

RE: [uml-devel] gcc-4.6.0 generates no code for sub_preempt_count()

[James McMechan]

> Am Donnerstag 14 April 2011, 09:49:14 schrieb Mikael Pettersson:
> > Richard Weinberger writes:
> > > Hi,
> > >
> > > I'm facing a very strange issue with gcc-4.6.0 and UML.
> > > Within __local_bh_enable() gcc generates no code for
> > > sub_preempt_count().
> > >
> > > See:
> > > http://userweb.kernel.org/~rw/uml-gcc460/__local_bh_enable-gcc460.txt
> > > vs.
> > > http://userweb.kernel.org/~rw/uml-gcc460/__local_bh_enable-gcc431.txt
> > >
> > > Interestingly it generates code for add_preempt_count().
> > > I can reproduce this on x86 and x86_64.
> > >
> > > The problem has to do with UML's current_thread_info() function.
> > > When I replace it with arch/x86's (unportable) variant gcc generates
> > > code.
> > >
> > > Any ideas whether this is a gcc or a kernel issue?

It looks like a gcc error with one of the optimization passes

> > Please provide a standalone test case.
>
> There you go!
> http://userweb.kernel.org/~rw/uml-gcc460/testcase.c

Replacing inline with __attribute__((noinline)) makes it produce code again

without requiring asm("esp")/asm("rsp") tricks and the code appears to be working

I think gcc is assuming only low bits in the address of stack vars and thought they

were all masked out :( with this change my test version of gcc-4.6.0 works for x86/amd64

I have not yet gotten 4.6.0 to install yet so I was testing with xgcc from the failed build


--- testcase.orig       2011-04-14 08:34:24.000000000 -0700

+++ testcase.c  2011-04-14 12:17:44.000000000 -0700

@@ -31,7 +31,7 @@

 }

 #else

 /* UML */

-static inline struct thread_info *current_thread_info(void)

+static __attribute__((noinline)) struct thread_info *current_thread_info(void)

 {

   struct thread_info *ti;

   unsigned long mask = THREAD_SIZE - 1;>

> Thanks,
> //richard

 		 	   		  

Re: [uml-devel] gcc-4.6.0 generates no code for sub_preempt_count()

[James McMechan]

> Am Donnerstag 14 April 2011, 09:49:14 schrieb Mikael Pettersson:
> > Richard Weinberger writes:
> > > Hi,
> > >
> > > I'm facing a very strange issue with gcc-4.6.0 and UML.
> > > Within __local_bh_enable() gcc generates no code for
> > > sub_preempt_count().
> > >
> > > See:
> > > http://userweb.kernel.org/~rw/uml-gcc460/__local_bh_enable-gcc460.txt
> > > vs.
> > > http://userweb.kernel.org/~rw/uml-gcc460/__local_bh_enable-gcc431.txt
> > >
> > > Interestingly it generates code for add_preempt_count().
> > > I can reproduce this on x86 and x86_64.
> > >
> > > The problem has to do with UML's current_thread_info() function.
> > > When I replace it with arch/x86's (unportable) variant gcc generates
> > > code.
> > >
> > > Any ideas whether this is a gcc or a kernel issue?

It looks like a gcc error with one of the optimization passes

> > Please provide a standalone test case.
>
> There you go!
> http://userweb.kernel.org/~rw/uml-gcc460/testcase.c

Replacing inline with __attribute__((noinline)) makes it produce code again

without requiring asm("esp")/asm("rsp") tricks and the code appears to be working

I think gcc is assuming only low bits in the address of stack vars and thought they

were all masked out :( with this change my test version of gcc-4.6.0 works for x86/amd64

I have not yet gotten 4.6.0 to install yet so I was testing with xgcc from the failed build


--- testcase.orig       2011-04-14 08:34:24.000000000 -0700

+++ testcase.c  2011-04-14 12:17:44.000000000 -0700

@@ -31,7 +31,7 @@

 }

 #else

 /* UML */

-static inline struct thread_info *current_thread_info(void)

+static __attribute__((noinline)) struct thread_info *current_thread_info(void)

 {

   struct thread_info *ti;

   unsigned long mask = THREAD_SIZE - 1;>

> Thanks,
> //richard

 		 	   		  
------------------------------------------------------------------------------
Benefiting from Server Virtualization: Beyond Initial Workload 
Consolidation -- Increasing the use of server virtualization is a top
priority.Virtualization can reduce costs, simplify management, and improve 
application availability and disaster protection. Learn more about boosting 
the value of server virtualization. http://p.sf.net/sfu/vmware-sfdev2dev
_______________________________________________
User-mode-linux-devel mailing list
User-mode-linux-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel

Re: [uml-devel] gcc-4.6.0 generates no code for sub_preempt_count()

[Richard Weinberger]

Am Donnerstag 14 April 2011, 21:50:13 schrieb James McMechan:
> > > > Any ideas whether this is a gcc or a kernel issue?
> 
> It looks like a gcc error with one of the optimization passes

I've submitted a bug report.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48623

Thanks,
//richard

Re: gcc-4.6.0 generates no code for sub_preempt_count()

[masterkom masterkom]

Hi,, I have the project to make Operating System using linux kernel.
That system is multiplatform, which is combine linux and window . This
project hope All people that who has familiar with windows can use
this operating system without sin. This project is free..

I hape there people can help us to done this project ,, thx,,,

On 4/14/11, Richard Weinberger <richard@nod.at> wrote:
> Hi,
>
> I'm facing a very strange issue with gcc-4.6.0 and UML.
> Within __local_bh_enable() gcc generates no code for sub_preempt_count().
>
> See:
> http://userweb.kernel.org/~rw/uml-gcc460/__local_bh_enable-gcc460.txt
> vs.
> http://userweb.kernel.org/~rw/uml-gcc460/__local_bh_enable-gcc431.txt
>
> Interestingly it generates code for add_preempt_count().
> I can reproduce this on x86 and x86_64.
>
> The problem has to do with UML's current_thread_info() function.
> When I replace it with arch/x86's (unportable) variant gcc generates code.
>
> Any ideas whether this is a gcc or a kernel issue?
> Thanks,
> //richard
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/
>

Re: gcc-4.6.0 generates no code for sub_preempt_count()

[Frank Kingswood]

On 14/04/11 15:43, masterkom masterkom wrote:
> Hi,, I have the project to make Operating System using linux kernel.
> That system is multiplatform, which is combine linux and window . This
> project hope All people that who has familiar with windows can use
> this operating system without sin. This project is free..

Well, good luck with that.
There was this Finish guy who wanted to do this, never heard from him again.

Frank