PAGE_SIZE is not guaranteed to be equal to or less than 8 times the THREAD_SIZE.
E.g. architecture hexagon may have page size 1M and thread size 4096. This would lead to a division by zero. The futex implementation assumes that tids fit into the FUTEX_TID_MASK. This limits the number of allowable threads. version 2: * use div64_u64 * check against FUTEX_TID_MASK Signed-off-by: Heinrich Schuchardt <[email protected]> --- kernel/fork.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/kernel/fork.c b/kernel/fork.c index cf65139..1449923 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -74,6 +74,7 @@ #include <linux/uprobes.h> #include <linux/aio.h> #include <linux/compiler.h> +#include <linux/math64.h> #include <asm/pgtable.h> #include <asm/pgalloc.h> @@ -255,6 +256,8 @@ void __init __weak arch_task_cache_init(void) { } void __init fork_init(unsigned long mempages) { + u64 temp; + #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR #ifndef ARCH_MIN_TASKALIGN #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES @@ -273,7 +276,16 @@ void __init fork_init(unsigned long mempages) * value: the thread structures can take up at most half * of memory. */ - max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); + temp = div64_u64((u64) mempages * (u64) PAGE_SIZE, + (u64) THREAD_SIZE * 8UL); + + /* + * The futex code assumes that tids fit into the FUTEX_TID_MASK. + */ + if (temp < FUTEX_TID_MASK) + max_threads = temp; + else + max_threads = FUTEX_TID_MASK; /* * we need to allow at least 20 threads to boot a system -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
