PR #3451 introduced a fatal bug which shows only in release mode, on RP2 / RP2350

[rgrr]

Operating System

PicoSDK

Commit SHA

80b2078

Board

Pico2

Firmware

My project uses TinyUSB with lots of interfaces, project is https://github.com/rgrr/yapicoprobe/

Problem appears on an RP2350 Pico2 board.

Not sure if it also will happen with an RP2040 board.

What happened ?

Updating TinyUSB from 0.20.0 to recent master showed a bug which crashes my device after some seconds after a reset. I guess this is the time of USB handshaking.

Surprisingly this happens only in release mode with gcc. gcc-debug, clang-debug and clang-release all run fine.

The problem had been introduced with #3451 (12.01.2026). The previous master containing #3448 (09.01.2026) runs also with gcc-release.

Any idea what could be the reason? Any hint how I can dig?

used compiler:

gcc 14.2.1
clang 21.1.1

How to reproduce ?

Difficult... question is more: how can I support finding this?

Debug Log as txt file (LOG/CFG_TUSB_DEBUG=2)

AFAICS there is no logging in this area.

Screenshots

No response

I have checked existing issues, discussion and documentation

• I confirm I have checked existing issues, discussion and documentation.

[hathach]

can you give a quick try if disable hwfifo would resolve this https://github.com/hathach/tinyusb/tree/rp2-disable-hwifo. If yes, it is probably a race condition.

[rgrr]

yes, problem disappears on the branch

[hathach]

@rgrr Thank you for confirmation, I guess the feature is not ready yet. Since I don't have the time to test it out, I will just disable it for now and re-enable later.

[rgrr]

Let me hear when you restart development in this direction so that I could help if wanted/required

[HiFiPhile]

For info some devs have been done: #3561 #3585 #3582

[rgrr]

For info some devs have been done: #3561 #3585 #3582

gosh... that's been a lot of work. Everything seems to work fine for rp2350 now, rp2040 not tested.

I close my complaint for now. Thanks for your great work!