Crash when calling `enumerate` from different threads (not simultaneously) - arm64 macOS

[afilini]

Crash when calling `enumerate` from different threads (not simultaneously) - arm64 macOS

[prusnak]

AFAIk hidapi is not thread-safe on neither of supported platforms

[afilini]

Do you have any links/documentation where they talk about thread safety? I find it very weird that it crashes even when the threads are properly synchronized. And it only happens in one specific os/arch combination, not on x86 macos or arm linux.

[prusnak]

Hm, I might be wrong. I only found this 11 years old comment: signal11/hidapi#56 (comment)

On Linux and Mac, HIDAPI is fully thread-safe.

On Windows, it mostly is. You should be able to read and write at the same time like you're saying. One thing that won't work is using hid_close() to stop a hid_read() which is on another thread.

[prusnak]

@afilini do you see the same failure with the following code?

import hid
import threading

def e():
    m.acquire()
    print(hid.enumerate())
    m.release()

m = threading.Lock()

a = threading.Thread(target=e, args=())
b = threading.Thread(target=e, args=())
c = threading.Thread(target=e, args=())

a.start()
b.start()
c.start()

a.join()
b.join()
c.join()

If yes, we can close this issue and open a new one in https://github.com/trezor/cython-hidapi because the issue is not in hwi but rather in cython-hidapi.

[afilini]

Yep, same issue

[achow101]

Closing as this is an usptream issue.

[prusnak]

Created trezor/cython-hidapi#148 to continue there