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SubjectRe: [PATCH 4/4] compat: add some tracing backport work
On Tue, Mar 20, 2012 at 6:53 AM, Luis R. Rodriguez <mcgrof@frijolero.org> wrote:
> On Tue, Mar 20, 2012 at 5:16 AM, Johannes Berg
> <johannes@sipsolutions.net> wrote:
> Sure, yeah I think I tried disabling as you suggested and ran into
> compilation issues with mac80211 on 2.6.31.

I tested again by only having this:


mcgrof@tux ~/compat (git::master)$ cat include/linux/tracepoint.h
#ifndef _COMPAT_LINUX_TRACEPOINT_H
#define _COMPAT_LINUX_TRACEPOINT_H 1

#include <linux/version.h>

#if (LINUX_VERSION_CODE > KERNEL_VERSION(2,6,33))
#include_next <linux/tracepoint.h>

#else /* just disable tracing */
/* Disable all tracing */
#undef TRACE_EVENT
#define TRACE_EVENT(name, proto, ...) \
static inline void trace_ ## name(proto) {}
#undef DECLARE_EVENT_CLASS
#define DECLARE_EVENT_CLASS(...)
#undef DEFINE_EVENT
#define DEFINE_EVENT(evt_class, name, proto, ...) \
static inline void trace_ ## name(proto) {}
#endif /* (LINUX_VERSION_CODE > KERNEL_VERSION(2,6,33)) */
#endif /* _COMPAT_LINUX_TRACEPOINT_H */
And then by using compat-wireless tag
compat-wireless-2012-03-14-3-g98cc995 against linux-next tag
next-20120314 I can only compile up to 2.6.34. Anything older I get
compilation errors which seem to point to somehow DEFINE_EVENT()
failing.

./scripts/gen-compat-autoconf.sh
/home/mcgrof/devel/compat-wireless/.config
/home/mcgrof/devel/compat-wireless/config.mk >
include/linux/compat_autoconf.h
make -C /lib/modules/2.6.33-02063305-generic/build
M=/home/mcgrof/devel/compat-wireless modules
make[1]: Entering directory `/usr/src/linux-headers-2.6.33-02063305-generic'
CC [M] /home/mcgrof/devel/compat-wireless/compat/main.o
In file included from include/linux/kmemtrace.h:12:0,
from include/linux/slub_def.h:13,
from include/linux/slab.h:162,
from include/linux/percpu.h:5,
from
/usr/src/linux-headers-2.6.33-02063305-generic/arch/x86/include/asm/local.h:4,
from include/linux/module.h:20,
from include/linux/textsearch.h:7,
from include/linux/skbuff.h:27,
from include/linux/if_ether.h:124,
from include/linux/netdevice.h:29,
from
/home/mcgrof/devel/compat-wireless/include/linux/compat-2.6.29.h:5,
from
/home/mcgrof/devel/compat-wireless/include/linux/compat-2.6.h:49,
from <command-line>:1:
include/trace/events/kmem.h:81:11: error: expected ‘)’ before ‘(’ token

Now this kmem.h line 81 has:

DEFINE_EVENT(kmem_alloc, kmalloc,

TP_PROTO(unsigned long call_site, const void *ptr,
size_t bytes_req, size_t bytes_alloc, gfp_t gfp_flags),

TP_ARGS(call_site, ptr, bytes_req, bytes_alloc, gfp_flags)
);

This is then fixed by adding TP_PROTO and TP_ARGS to our backport:

#define TP_PROTO(args...) args
#define TP_ARGS(args...) args
#define TP_CONDITION(args...) args

But then we get:

./scripts/gen-compat-autoconf.sh
/home/mcgrof/devel/compat-wireless/.config
/home/mcgrof/devel/compat-wireless/config.mk >
include/linux/compat_autoconf.h
make -C /lib/modules/2.6.33-02063305-generic/build
M=/home/mcgrof/devel/compat-wireless modules
make[1]: Entering directory `/usr/src/linux-headers-2.6.33-02063305-generic'
CC [M] /home/mcgrof/devel/compat-wireless/compat/main.o
In file included from include/linux/kmemtrace.h:12:0,
from include/linux/slub_def.h:13,
from include/linux/slab.h:162,
from include/linux/percpu.h:5,
from
/usr/src/linux-headers-2.6.33-02063305-generic/arch/x86/include/asm/local.h:4,
from include/linux/module.h:20,
from include/linux/textsearch.h:7,
from include/linux/skbuff.h:27,
from include/linux/if_ether.h:124,
from include/linux/netdevice.h:29,
from
/home/mcgrof/devel/compat-wireless/include/linux/compat-2.6.29.h:5,
from
/home/mcgrof/devel/compat-wireless/include/linux/compat-2.6.h:49,
from <command-line>:1:
include/trace/events/kmem.h:292:41: error: expected ‘)’ before ‘(’ token

And also:

include/linux/module.h:543:47: warning: ‘struct tracepoint_iter’
declared inside parameter list
include/linux/module.h:543:47: warning: its scope is only this
definition or declaration, which is probably not what you want
make[3]: *** [/home/mcgrof/devel/compat-wireless/compat/main.o] Error 1
make[2]: *** [/home/mcgrof/devel/compat-wireless/compat] Error 2
make[1]: *** [_module_/home/mcgrof/devel/compat-wireless] Error 2
make[1]: Leaving directory `/usr/src/linux-headers-2.6.33-02063305-generic'
make: *** [modules] Error 2

I'm trying to work my way through disabling this properly but haven't
figured out yet how. I tried adding:

#undef DECLARE_TRACE
#define DECLARE_TRACE(name, proto, ...) \
static inline void trace_ ## name(proto) {}
#undef DEFINE_EVENT_PRINT
#define DEFINE_EVENT_PRINT(template, name, proto, args, print) \
DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))

But no dice. I then figured it may be my kernel with
CONFIG_TRACEPOINTS=y and indeed that is the case -- so we have to
consider the case where the target kernel may have tracing enabled and
we have to disable it somehow. Undef'ing CONFIG_TRACEPOINTS and
DECLARE_TRACE doesn't really do it.

We may need to redefine each macro to some COMPAT_TRACE_ macro, not sure yet.

Luis
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