Messages in this thread Patch in this message | | | Date | Tue, 11 Mar 2008 02:30:14 +0100 | From | Andi Kleen <> | Subject | [PATCH REPOST for 2.6.25] Use an own random generator for pageattr-test.c |
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Use an own random generator for pageattr-test.c
[Repost. Please ack/nack. This is a bug fix and imho a .25 late merge candidate because it fixes a subtle bug]
pageattr-test attempts to be repeatable and uses srandom32 to get a repeatable random number sequence.
Using srandom32() wasn't a good idea for various reasons: - it is per cpu and if the cpu changes on a preemptible kernel it gets lost - networking and random32 puts in some own state - srandom32() does not actually reset the state, but just adds bits to it
Instead use a very simple private standard rnd that gives repeatable results. I took the reference rand() from ISO-C.
Signed-off-by: Andi Kleen <ak@suse.de>
--- arch/x86/mm/pageattr-test.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
Index: linux/arch/x86/mm/pageattr-test.c =================================================================== --- linux.orig/arch/x86/mm/pageattr-test.c +++ linux/arch/x86/mm/pageattr-test.c @@ -101,6 +101,14 @@ static int print_split(struct split_stat static unsigned long addr[NTEST]; static unsigned int len[NTEST]; +static int next = 100; + +static unsigned my_rand(void) +{ + next = next * 1103515245 + 12345; + return next; +} + /* Change the global bit on random pages in the direct mapping */ static int pageattr_test(void) { @@ -123,10 +131,9 @@ static int pageattr_test(void) memset(bm, 0, (max_pfn_mapped + 7) / 8); failed += print_split(&sa); - srandom32(100); for (i = 0; i < NTEST; i++) { - unsigned long pfn = random32() % max_pfn_mapped; + unsigned long pfn = my_rand() % max_pfn_mapped; addr[i] = (unsigned long)__va(pfn << PAGE_SHIFT); len[i] = random32() % 100;
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