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[PATCH 2/7] liblockdep: Reduce MAX_LOCK_DEPTH to avoid overflowing lock_chain::depth

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liblockdep has been broken since commit 75dd602a5198 ("lockdep: Fix
lock_chain::base size"), as that adds a check that MAX_LOCK_DEPTH is
within the range of lock_chain::depth and in liblockdep it is much
too large.

That should have resulted in a compiler error, but didn't because:

- the check uses ARRAY_SIZE(), which isn't yet defined in liblockdep
  so is assumed to be an (undeclared) function
- putting a function call inside a BUILD_BUG_ON() expression quietly
  turns it into some nonsense involving a variable-length array

It did produce a compiler warning, but I didn't notice because
liblockdep already produces too many warnings if -Wall is enabled
(which I'll fix shortly).

Even before that commit, which reduced lock_chain::depth from 8 bits
to 6, MAX_LOCK_DEPTH was too large.

Cc: <stable@vger.kernel.org> # for versions before 4.6, use a value of 255
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 tools/lib/lockdep/uinclude/linux/lockdep.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/lockdep/uinclude/linux/lockdep.h b/tools/lib/lockdep/uinclude/linux/lockdep.h
index c808c7d02d21..d30214221920 100644
--- a/tools/lib/lockdep/uinclude/linux/lockdep.h
+++ b/tools/lib/lockdep/uinclude/linux/lockdep.h
@@ -8,7 +8,7 @@
 #include <linux/utsname.h>
 #include <linux/compiler.h>
 
-#define MAX_LOCK_DEPTH 2000UL
+#define MAX_LOCK_DEPTH 63UL
 
 #define asmlinkage
 #define __visible

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[PATCH 0/7] Fixes for liblockdep Ben Hutchings <ben@decadent.org.uk> - 2016-06-14 22:50 +0200
  [PATCH 3/7] liblockdep: Define the ARRAY_SIZE() macro Ben Hutchings <ben@decadent.org.uk> - 2016-06-14 22:50 +0200
  [PATCH 5/7] liblockdep: Fix 'unused value' warnings Ben Hutchings <ben@decadent.org.uk> - 2016-06-14 22:50 +0200
  [PATCH 4/7] liblockdep: Enable -Wall by default Ben Hutchings <ben@decadent.org.uk> - 2016-06-14 22:50 +0200
  [PATCH 1/7] liblockdep: Fix undefined symbol prandom_u32 Ben Hutchings <ben@decadent.org.uk> - 2016-06-14 22:50 +0200
    Re: [PATCH 1/7] liblockdep: Fix undefined symbol prandom_u32 Sasha Levin <sasha.levin@oracle.com> - 2016-06-14 23:40 +0200
  [PATCH 2/7] liblockdep: Reduce MAX_LOCK_DEPTH to avoid overflowing  lock_chain::depth Ben Hutchings <ben@decadent.org.uk> - 2016-06-14 22:50 +0200
    Re: [PATCH 2/7] liblockdep: Reduce MAX_LOCK_DEPTH to avoid  overflowing lock_chain::depth Peter Zijlstra <peterz@infradead.org> - 2016-06-14 23:20 +0200
  Re: [PATCH 0/7] Fixes for liblockdep Sasha Levin <sasha.levin@oracle.com> - 2016-06-14 23:40 +0200

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