From 878ab0f7c084d22ecbca25953907f637474c70d9 Mon Sep 17 00:00:00 2001 From: Arjan van de Ven Date: Sat, 8 May 2010 15:47:37 -0700 Subject: cpuidle: Fix incorrect optimization commit 1c6fe0364fa7bf28248488753ee0afb6b759cd04 upstream. commit 672917dcc78 ("cpuidle: menu governor: reduce latency on exit") added an optimization, where the analysis on the past idle period moved from the end of idle, to the beginning of the new idle. Unfortunately, this optimization had a bug where it zeroed one key variable for new use, that is needed for the analysis. The fix is simple, zero the variable after doing the work from the previous idle. During the audit of the code that found this issue, another issue was also found; the ->measured_us data structure member is never set, a local variable is always used instead. Signed-off-by: Arjan van de Ven Cc: Corrado Zoccolo Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- drivers/cpuidle/governors/menu.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c index 73655aeb3a60..f8e57c6303f2 100644 --- a/drivers/cpuidle/governors/menu.c +++ b/drivers/cpuidle/governors/menu.c @@ -101,7 +101,6 @@ struct menu_device { unsigned int expected_us; u64 predicted_us; - unsigned int measured_us; unsigned int exit_us; unsigned int bucket; u64 correction_factor[BUCKETS]; @@ -187,14 +186,14 @@ static int menu_select(struct cpuidle_device *dev) int i; int multiplier; - data->last_state_idx = 0; - data->exit_us = 0; - if (data->needs_update) { menu_update(dev); data->needs_update = 0; } + data->last_state_idx = 0; + data->exit_us = 0; + /* Special case when user has set very strict latency requirement */ if (unlikely(latency_req == 0)) return 0; @@ -294,7 +293,7 @@ static void menu_update(struct cpuidle_device *dev) new_factor = data->correction_factor[data->bucket] * (DECAY - 1) / DECAY; - if (data->expected_us > 0 && data->measured_us < MAX_INTERESTING) + if (data->expected_us > 0 && measured_us < MAX_INTERESTING) new_factor += RESOLUTION * measured_us / data->expected_us; else /* -- cgit v1.2.3