Idle CPU Usage of usbmuxd

Installing and Using OpenWrt
1

Using 22.03.2 r19803-9a599fee93 on WNDR3700v1 as a backup cellular WAN router.

Even when a phone isn't connected, usbmuxd is eating up 30-40% of cpu. I tried rebooting without ever connecting a phone and the issue persists. I tried killing and restarting usbmuxd and that didn't help either.

1 Like
2

Hi, has this issue been resolved?

3

My framework is openwrt-22.03.2/target/linux/ath79

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image1102×748 311 KB

4

still there, hovers between 20-40%:

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image820×916 40.6 KB

5

I found the reason is because of the "HAVE_PPOLL" macro definition in the usbmuxd package
Removing this macro definition will fix it

64BD36D1-953E-44b2-90AE-F8E7CC89D924
64BD36D1-953E-44b2-90AE-F8E7CC89D9241469×362 17.4 KB

1 Like
6

what does HAVE_PPOLL macro do?

7

你可以用以下命令调试：
/etc/init.d/usbmuxd stop
usbmuxd -f -vvvv

8

English, please.

You can debug with the following command:

9

I am not an expert in debugging openwrt code. Are you saying that this polling is not necessary for usb tethering?

10

Normally polling would wait 100s, but it didn't

11

If this is a bug do I need to report it somewhere else?

12

what architecture is your cpu
I'm not sure if it's caused by the architecture
mine is ipq40xx

13

No idea, whatever architecture wndr3700v1 is :slight_smile:

14

For Netgear WNDR3700V1 it's ar71xx (Atheros AR7161).

15

Here is the culprit:

struct timespec
{
	time_t tv_sec;
	long int tv_nsec;
};

If usbmuxd is compiled with 64 bit time_t, but ppoll expects it to be 32 bit, the following timespec data is interpreted by ppoll:

// little endianness: timeout is 100 seconds
int32_t tv_sec = 100;
int32_t tv_nsec = 0;
int32_t unused = 0;

// big endianness: timeout is 100 nano-seconds
int32_t tv_sec = 0;
int32_t tv_nsec = 100;
int32_t unused = 0;

I was able to confirm this by defining a timespec32 structure, setting tv_sec = 1 and then casting its pointer to (struct timespec *). This results in timeouts of 1 second as expected. Only big endianness CPUs are affected. That's why I have no issues with WRT3200ACM, while the old TL-WR1043ND is affected.
Before I submit a patch, I need to find why usbmuxd is compiled with 64 bit time_t and change it to match ppoll. This looks like wrong include paths or incorrect macros.

Edit: issue and fix

1 Like
16

thank you.

17

Fixed on master. Expect a backport to 22.03 soon. :beers: