From 70c50ee72eebb3d1e3aae7450269fd8d8074c610 Mon Sep 17 00:00:00 2001 From: Petr Mladek Date: Fri, 5 Aug 2016 15:20:41 +0200 Subject: thermal/powerclamp: Prevent division by zero when counting interval I have got a zero division error when disabling the forced idle injection from the intel powerclamp. I did echo 0 >/sys/class/thermal/cooling_device48/cur_state and got [ 986.072632] divide error: 0000 [#1] PREEMPT SMP [ 986.078989] Modules linked in: [ 986.083618] CPU: 17 PID: 24967 Comm: kidle_inject/17 Not tainted 4.7.0-1-default+ #3055 [ 986.093781] Hardware name: Intel Corporation S2600CP/S2600CP, BIOS RMLSDP.86I.R3.27.D685.1305151734 05/15/2013 [ 986.106227] task: ffff880430e1c080 task.stack: ffff880427ef0000 [ 986.114122] RIP: 0010:[] [] clamp_thread+0x1d9/0x600 [ 986.124609] RSP: 0018:ffff880427ef3e20 EFLAGS: 00010246 [ 986.131860] RAX: 0000000000000258 RBX: 0000000000000006 RCX: 0000000000000001 [ 986.141179] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000018 [ 986.150478] RBP: ffff880427ef3ec8 R08: ffff880427ef0000 R09: 0000000000000002 [ 986.159779] R10: 0000000000003df2 R11: 0000000000000018 R12: 0000000000000002 [ 986.169089] R13: 0000000000000000 R14: ffff880427ef0000 R15: ffff880427ef0000 [ 986.178388] FS: 0000000000000000(0000) GS:ffff880435940000(0000) knlGS:0000000000000000 [ 986.188785] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 986.196559] CR2: 00007f1d0caf0000 CR3: 0000000002006000 CR4: 00000000001406e0 [ 986.205909] Stack: [ 986.209524] ffff8802be897b00 ffff880430e1c080 0000000000000011 0000006a35959780 [ 986.219236] 0000000000000011 ffff880427ef0008 0000000000000000 ffff8804359503d0 [ 986.228966] 0000000100029d93 ffffffff81794140 0000000000000000 ffffffff05000011 [ 986.238686] Call Trace: [ 986.242825] [] ? pkg_state_counter+0x80/0x80 [ 986.250866] [] ? powerclamp_set_cur_state+0x180/0x180 [ 986.259797] [] kthread+0xc9/0xe0 [ 986.266682] [] ret_from_fork+0x1f/0x40 [ 986.274142] [] ? kthread_create_on_node+0x180/0x180 [ 986.282869] Code: d1 ea 48 89 d6 80 3d 6a d0 d4 00 00 ba 64 00 00 00 89 d8 41 0f 45 f5 0f af c2 42 8d 14 2e be 31 00 00 00 83 fa 31 0f 42 f2 31 d2 f6 48 8b 15 9e 07 87 00 48 8b 3d 97 07 87 00 48 63 f0 83 e8 [ 986.307806] RIP [] clamp_thread+0x1d9/0x600 [ 986.315871] RSP RIP points to the following lines: compensation = get_compensation(target_ratio); interval = duration_jiffies*100/(target_ratio+compensation); A solution would be to switch the following two commands in powerclamp_set_cur_state(): set_target_ratio = 0; end_power_clamp(); But I think that the zero division might happen also when target_ratio is non-zero because the compensation might be negative. Therefore we also check the sum of target_ratio and compensation explicitly. Also the compensated_ratio variable is always set. Therefore there is no need to initialize it. Signed-off-by: Petr Mladek Acked-by: Jacob Pan Signed-off-by: Zhang Rui diff --git a/drivers/thermal/intel_powerclamp.c b/drivers/thermal/intel_powerclamp.c index 015ce2e..0e4dc0a 100644 --- a/drivers/thermal/intel_powerclamp.c +++ b/drivers/thermal/intel_powerclamp.c @@ -388,7 +388,7 @@ static int clamp_thread(void *arg) int sleeptime; unsigned long target_jiffies; unsigned int guard; - unsigned int compensation = 0; + unsigned int compensated_ratio; int interval; /* jiffies to sleep for each attempt */ unsigned int duration_jiffies = msecs_to_jiffies(duration); unsigned int window_size_now; @@ -409,8 +409,11 @@ static int clamp_thread(void *arg) * c-states, thus we need to compensate the injected idle ratio * to achieve the actual target reported by the HW. */ - compensation = get_compensation(target_ratio); - interval = duration_jiffies*100/(target_ratio+compensation); + compensated_ratio = target_ratio + + get_compensation(target_ratio); + if (compensated_ratio <= 0) + compensated_ratio = 1; + interval = duration_jiffies * 100 / compensated_ratio; /* align idle time */ target_jiffies = roundup(jiffies, interval); @@ -647,8 +650,8 @@ static int powerclamp_set_cur_state(struct thermal_cooling_device *cdev, goto exit_set; } else if (set_target_ratio > 0 && new_target_ratio == 0) { pr_info("Stop forced idle injection\n"); - set_target_ratio = 0; end_power_clamp(); + set_target_ratio = 0; } else /* adjust currently running */ { set_target_ratio = new_target_ratio; /* make new set_target_ratio visible to other cpus */ -- cgit v0.10.2