Messages in this thread Patch in this message | | | Subject | Re: [PATCH] Fix cpu iterator on empty bitmask | From | Rusty Russell <> | Date | Wed, 28 Apr 2004 11:22:28 +1000 |
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On Wed, 2004-04-28 at 10:05, William Lee Irwin III wrote: > On Wed, Apr 28, 2004 at 09:52:53AM +1000, Rusty Russell wrote: > > Name: Fix cpumask iterator over empty cpu set > > Status: Trivial > > Can't use _ffs() without first checking for zero, and if bits beyond > > NR_CPUS set it'll give bogus results. Use find_first_bit > > I sent in something equivalent to this along with a number of other > fixes (cpus_shift_right() leaking junk bits in in and cpus_weight() > and cpus_empty() and cpus_equal() and the like not ignoring tails) and > got a NAK since it clashes with something Paul Jackson's doing.
Agreed, I'm pretty sure Paul's work doesn't make this mistake, but this is a trivial patch for a real big which is causing oopses today.
Linus, please apply... Rusty.
Name: Fix cpumask iterator over empty cpu set Status: Trivial
Can't use _ffs() without first checking for zero, and if bits beyond NR_CPUS set it'll give bogus results. Use find_first_bit
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .26180-linux-2.6.6-rc2-bk5/include/asm-generic/cpumask_arith.h .26180-linux-2.6.6-rc2-bk5.updated/include/asm-generic/cpumask_arith.h --- .26180-linux-2.6.6-rc2-bk5/include/asm-generic/cpumask_arith.h 2004-01-10 13:59:33.000000000 +1100 +++ .26180-linux-2.6.6-rc2-bk5.updated/include/asm-generic/cpumask_arith.h 2004-04-28 09:50:23.000000000 +1000 @@ -43,7 +43,7 @@ #define cpus_promote(map) ({ map; }) #define cpumask_of_cpu(cpu) ({ ((cpumask_t)1) << (cpu); }) -#define first_cpu(map) __ffs(map) +#define first_cpu(map) find_first_bit(&(map), NR_CPUS) #define next_cpu(cpu, map) find_next_bit(&(map), NR_CPUS, cpu + 1) #endif /* __ASM_GENERIC_CPUMASK_ARITH_H */ -- Anyone who quotes me in their signature is an idiot -- Rusty Russell
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