From: Ingo Molnar <mingo@elte.hu>
Date: Thu, 19 Mar 2009 12:21:44 +0000 (+0100)
Subject: symbols, stacktrace: look up init symbols after module symbols
X-Git-Tag: v2.6.30-rc1~213^2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4a44bac1f98223ed77e47bf3b42fcfd10cddd85f;p=pandora-kernel.git

symbols, stacktrace: look up init symbols after module symbols

Impact: fix incomplete stacktraces

I noticed such weird stacktrace entries in lockdep dumps:

[    0.285956] {HARDIRQ-ON-W} state was registered at:
[    0.285956]   [<ffffffff802bce90>] mark_irqflags+0xbe/0x125
[    0.285956]   [<ffffffff802bf2fd>] __lock_acquire+0x674/0x82d
[    0.285956]   [<ffffffff802bf5b2>] lock_acquire+0xfc/0x128
[    0.285956]   [<ffffffff8135b636>] rt_spin_lock+0xc8/0xd0
[    0.285956]   [<ffffffffffffffff>] 0xffffffffffffffff

The stacktrace entry is cut off after rt_spin_lock.

After much debugging i found out that stacktrace entries that
belong to init symbols dont get printed out, due to commit:

  a2da405: module: Don't report discarded init pages as kernel text.

The reason is this check added to core_kernel_text():

-       if (addr >= (unsigned long)_sinittext &&
+       if (system_state == SYSTEM_BOOTING &&
+           addr >= (unsigned long)_sinittext &&
            addr <= (unsigned long)_einittext)
                return 1;

This will discard inittext symbols even though their symbol table
is still present and even though stacktraces done while the system
was booting up might still be relevant.

To not reintroduce the (not well-specified) bug addressed in that
commit, first do a module symbols lookup, then a final init-symbols
lookup.

This will work fine on architectures that have separate address
spaces for modules (such as x86) - and should not crash any other
architectures either.

Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
LKML-Reference: <new-discussion>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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