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alpha: fix 32/64-bit bug in futex support
Michael Cree said: : : I have noticed some user space problems (pulseaudio crashes in pthread : : code, glibc/nptl test suite failures, java compiler freezes on SMP alpha : : systems) that arise when using a 2.6.39 or later kernel on Alpha. : : Bisecting between 2.6.38 and 2.6.39 (using glibc/nptl test suite as : : criterion for good/bad kernel) eventually leads to: : : : :8d7718aa08
is the first bad commit : : commit8d7718aa08
: : Author: Michel Lespinasse <walken@google.com> : : Date: Thu Mar 10 18:50:58 2011 -0800 : : : : futex: Sanitize futex ops argument types : : : : Change futex_atomic_op_inuser and futex_atomic_cmpxchg_inatomic : : prototypes to use u32 types for the futex as this is the data type the : : futex core code uses all over the place. : : : : Looking at the commit I see there is a change of the uaddr argument in : : the Alpha architecture specific code for futexes from int to u32, but I : : don't see why this should cause a problem. Richard Henderson said: : futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, : u32 oldval, u32 newval) : ... : : "r"(uaddr), "r"((long)oldval), "r"(newval) : : : There is no 32-bit compare instruction. These are implemented by : consistently extending the values to a 64-bit type. Since the : load instruction sign-extends, we want to sign-extend the other : quantity as well (despite the fact it's logically unsigned). : : So: : : - : "r"(uaddr), "r"((long)oldval), "r"(newval) : + : "r"(uaddr), "r"((long)(int)oldval), "r"(newval) : : should do the trick. Michael said: : This fixes the glibc test suite failures and the pulseaudio related : crashes, but it does not fix the java compiiler lockups that I was (and : are still) observing. That is some other problem. Reported-by: Michael Cree <mcree@orcon.net.nz> Tested-by: Michael Cree <mcree@orcon.net.nz> Acked-by: Phil Carmody <ext-phil.2.carmody@nokia.com> Cc: Richard Henderson <rth@twiddle.net> Cc: Michel Lespinasse <walken@google.com> Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru> Reviewed-by: Matt Turner <mattst88@gmail.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -108,7 +108,7 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
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" lda $31,3b-2b(%0)\n"
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" .previous\n"
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: "+r"(ret), "=&r"(prev), "=&r"(cmp)
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: "r"(uaddr), "r"((long)oldval), "r"(newval)
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: "r"(uaddr), "r"((long)(int)oldval), "r"(newval)
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: "memory");
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*uval = prev;
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