weird cooling_device/cur_state sysfs behaviour

[Willy Wolff <willy.mh.wolff.ml@gmail.com>]

Hi all,
Hope you're doing well with the situation.

I fill that my board get a cold too...

When I write to a sysfs node, I have a weird behaviour about the function that is called behind.
This bug appears on an arm32 odroid-xu3, and only after v5.4, v5.3.18 behave correctly.


Here my modification to see what's going on:

diff --git a/drivers/thermal/thermal_sysfs.c b/drivers/thermal/thermal_sysfs.c
index aa99edb4dff7..a437ae3f4b9f 100644
--- a/drivers/thermal/thermal_sysfs.c
+++ b/drivers/thermal/thermal_sysfs.c
@@ -706,11 +706,22 @@ cur_state_store(struct device *dev, struct device_attribute *attr,
        unsigned long state;
        int result;
 
-       if (sscanf(buf, "%ld\n", &state) != 1)
+       dump_stack();
+
+       printk(KERN_INFO "%s:%d:%s buf = \"%s\", count = %zu\n",
+              __FILE__, __LINE__, __func__, buf, count);
+
+       if (sscanf(buf, "%ld\n", &state) != 1) {
+               printk(KERN_INFO "%s:%d:%s\n",
+                      __FILE__, __LINE__, __func__);
                return -EINVAL;
+       }
 
-       if ((long)state < 0)
+       if ((long)state < 0) {
+               printk(KERN_INFO "%s:%d:%s\n",
+                      __FILE__, __LINE__, __func__);
                return -EINVAL;
+       }
 
        mutex_lock(&cdev->lock);
 
@@ -719,9 +730,14 @@ cur_state_store(struct device *dev, struct device_attribute *attr,
                thermal_cooling_device_stats_update(cdev, state);
 
        mutex_unlock(&cdev->lock);
+
+       printk(KERN_INFO "%s:%d:%s result = %d, count = %zu\n",
+              __FILE__, __LINE__, __func__, result, count);
+
        return result ? result : count;
 }
 
+
 static struct device_attribute
 dev_attr_cdev_type = __ATTR(type, 0444, cdev_type_show, NULL);
 static DEVICE_ATTR_RO(max_state);



And here the prob:
Thursday 2019-02-14 10:26:46 root@odroid-xu3-0 ~
$ echo 11 > /sys/devices/virtual/thermal/cooling_device1/cur_state                                                                                    
[  908.109955] CPU: 5 PID: 500 Comm: bash Not tainted 5.4.0-dirty #6
[  908.114910] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
[  908.121014] [<c0112f08>] (unwind_backtrace) from [<c010df38>] (show_stack+0x10/0x14)
[  908.128796] [<c010df38>] (show_stack) from [<c0ae89cc>] (dump_stack+0xa4/0xd0)
[  908.135962] [<c0ae89cc>] (dump_stack) from [<c0759e0c>] (cur_state_store+0x2c/0x14c)
[  908.143686] [<c0759e0c>] (cur_state_store) from [<c033b360>] (kernfs_fop_write+0x100/0x1e0)
[  908.152035] [<c033b360>] (kernfs_fop_write) from [<c02a93f4>] (__vfs_write+0x2c/0x1c0)
[  908.159908] [<c02a93f4>] (__vfs_write) from [<c02ac25c>] (vfs_write+0xa4/0x188)
[  908.167163] [<c02ac25c>] (vfs_write) from [<c02ac4b0>] (ksys_write+0x58/0xd0)
[  908.174242] [<c02ac4b0>] (ksys_write) from [<c0101000>] (ret_fast_syscall+0x0/0x28)
[  908.181874] Exception stack(0xeb915fa8 to 0xeb915ff0)
[  908.186800] 5fa0:                   00000074 0050ba08 00000001 0050ba08 00000003 00000000
[  908.195083] 5fc0: 00000074 0050ba08 b6eb3db0 00000004 00000003 00000003 00000000 00000000
[  908.203218] 5fe0: 00000004 bef3c830 b6e4b5b3 b6dd4746
[  908.210744] drivers/thermal/thermal_sysfs.c:712:cur_state_store buf = "11
[  908.210744] ", count = 3
[  908.221520] drivers/thermal/thermal_sysfs.c:735:cur_state_store result = 1, count = 3
[  908.228681] CPU: 5 PID: 500 Comm: bash Not tainted 5.4.0-dirty #6
[  908.234268] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
[  908.240372] [<c0112f08>] (unwind_backtrace) from [<c010df38>] (show_stack+0x10/0x14)
[  908.248159] [<c010df38>] (show_stack) from [<c0ae89cc>] (dump_stack+0xa4/0xd0)
[  908.255325] [<c0ae89cc>] (dump_stack) from [<c0759e0c>] (cur_state_store+0x2c/0x14c)
[  908.263048] [<c0759e0c>] (cur_state_store) from [<c033b360>] (kernfs_fop_write+0x100/0x1e0)
[  908.271398] [<c033b360>] (kernfs_fop_write) from [<c02a93f4>] (__vfs_write+0x2c/0x1c0)
[  908.279271] [<c02a93f4>] (__vfs_write) from [<c02ac25c>] (vfs_write+0xa4/0x188)
[  908.286527] [<c02ac25c>] (vfs_write) from [<c02ac4b0>] (ksys_write+0x58/0xd0)
[  908.293608] [<c02ac4b0>] (ksys_write) from [<c0101000>] (ret_fast_syscall+0x0/0x28)
[  908.301241] Exception stack(0xeb915fa8 to 0xeb915ff0)
[  908.306168] 5fa0:                   00000074 0050ba09 00000001 0050ba09 00000002 00000000
[  908.314448] 5fc0: 00000074 0050ba09 b6eb3db0 00000004 00000003 00000003 00000000 00000000
[  908.322581] 5fe0: 00000004 bef3c830 b6e4b5b3 b6dd4746
[  908.328660] drivers/thermal/thermal_sysfs.c:712:cur_state_store buf = "1
[  908.328660] ", count = 2
[  908.338432] drivers/thermal/thermal_sysfs.c:735:cur_state_store result = 1, count = 2
[  908.345695] CPU: 5 PID: 500 Comm: bash Not tainted 5.4.0-dirty #6
[  908.351172] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
[  908.357276] [<c0112f08>] (unwind_backtrace) from [<c010df38>] (show_stack+0x10/0x14)
[  908.365062] [<c010df38>] (show_stack) from [<c0ae89cc>] (dump_stack+0xa4/0xd0)
[  908.372227] [<c0ae89cc>] (dump_stack) from [<c0759e0c>] (cur_state_store+0x2c/0x14c)
[  908.379951] [<c0759e0c>] (cur_state_store) from [<c033b360>] (kernfs_fop_write+0x100/0x1e0)
[  908.388302] [<c033b360>] (kernfs_fop_write) from [<c02a93f4>] (__vfs_write+0x2c/0x1c0)
[  908.396176] [<c02a93f4>] (__vfs_write) from [<c02ac25c>] (vfs_write+0xa4/0x188)
[  908.403433] [<c02ac25c>] (vfs_write) from [<c02ac4b0>] (ksys_write+0x58/0xd0)
[  908.410511] [<c02ac4b0>] (ksys_write) from [<c0101000>] (ret_fast_syscall+0x0/0x28)
[  908.418145] Exception stack(0xeb915fa8 to 0xeb915ff0)
[  908.423068] 5fa0:                   00000074 0050ba0a 00000001 0050ba0a 00000001 00000000
[  908.431352] 5fc0: 00000074 0050ba0a b6eb3db0 00000004 00000003 00000003 00000000 00000000
[  908.439487] 5fe0: 00000004 bef3c830 b6e4b5b3 b6dd4746
[  908.445365] drivers/thermal/thermal_sysfs.c:712:cur_state_store buf = "
[  908.445365] ", count = 1
[  908.454762] drivers/thermal/thermal_sysfs.c:716:cur_state_store
-bash: echo: write error: Invalid argument




As you can see, the function is recalled with one character less, until the "buffer is empty".
I don't understand why. Can anybody help me for this thing?
Many thanks in advance.

Best Regards,
Willy