Messages in this thread Patch in this message | | | From | George Spelvin <> | Date | Fri, 29 Nov 2019 17:10:04 -0500 | Subject | [RFC PATCH v1 30/50] kernel/locking/test-ww_mutex.c: Use cheaper prandom_u32_max() |
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This is test code; it doesn't need crypto-quality random numbers.
Also use the simpler initialize-while-shuffling variant of the Fisher-Yates shuffle in get_random_order().
(It's not clear that we need the order[] array at all. Could we just shuffle the stress->locks array directly?)
Signed-off-by: George Spelvin <lkml@sdf.org> Cc: Thomas Hellstrom <thellstrom@vmware.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Will Deacon <will@kernel.org> --- kernel/locking/test-ww_mutex.c | 23 ++++++++--------------- 1 file changed, 8 insertions(+), 15 deletions(-)
diff --git a/kernel/locking/test-ww_mutex.c b/kernel/locking/test-ww_mutex.c index 3e82f449b4ff7..3fc54d88eb842 100644 --- a/kernel/locking/test-ww_mutex.c +++ b/kernel/locking/test-ww_mutex.c @@ -348,25 +348,18 @@ struct stress { static int *get_random_order(int count) { - int *order; - int n, r, tmp; + int n, *order; order = kmalloc_array(count, sizeof(*order), GFP_KERNEL); - if (!order) + if (!order || !count) return order; - for (n = 0; n < count; n++) - order[n] = n; - - for (n = count - 1; n > 1; n--) { - r = get_random_int() % (n + 1); - if (r != n) { - tmp = order[n]; - order[n] = order[r]; - order[r] = tmp; - } + order[0] = 0; + for (n = 1; n < count; n++) { + int r = prandom_u32_max(n+1); + order[n] = order[r]; + order[r] = n; } - return order; } @@ -498,7 +491,7 @@ static void stress_one_work(struct work_struct *work) { struct stress *stress = container_of(work, typeof(*stress), work); const int nlocks = stress->nlocks; - struct ww_mutex *lock = stress->locks + (get_random_int() % nlocks); + struct ww_mutex *lock = stress->locks + prandom_u32_max(nlocks); int err; do { -- 2.26.0
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