From 1c6fe0364fa7bf28248488753ee0afb6b759cd04 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 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 Cc: stable@kernel.org Signed-off-by: Linus Torvalds --- drivers/cpuidle/governors/menu.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) (limited to 'drivers') diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c index 1aea7157d8f..f8e57c6303f 100644 --- a/drivers/cpuidle/governors/menu.c +++ b/drivers/cpuidle/governors/menu.c @@ -100,7 +100,6 @@ struct menu_device { int needs_update; unsigned int expected_us; - unsigned int measured_us; u64 predicted_us; unsigned int exit_us; unsigned int bucket; @@ -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