[Console] fix: console deinit always deadlocks - adds ability to unblock linenoise (try 2) (IDFGH-9188)

[chipweinberger]

Previous PR: https://github.com/espressif/esp-idf/pull/9983

I am re-opening this PR to get more traction on it.

This solves: https://github.com/espressif/esp-idf/issues/9974

Motivation:

• currently, console deinit causes a deadlock
• without deinit, we can't create consoles "as needed"
• for example, USB Serial JTAG console should be destroyed when entering USB host mode
• for example, "web" consoles should be destroyed when the browser window is closed

[SoucheSouche]

Hi @chipweinberger, I started looking into your PR. Can I ask you to rebase and fix the build issues and conflict with upstream?

[chipweinberger]

sure, one moment.

[chipweinberger]

@SoucheSouche updated.

[CLAassistant]

All committers have signed the CLA.

[chipweinberger]

@SoucheSouche how are things going?

[SoucheSouche]

@chipweinberger, there has been some changes in the ring buffer so I am now looking at your PR again since the semaphores for rx and tx were removed.

But tomorrow is my last working day before my extended leaves so I will most likely not finish up before. Someone from my team will take over the console related PRs.

[chipweinberger]

since the semaphores for rx and tx were removed.

I updated the PR and removed the semaphores.

But as I was saying before I think we should move this bit: #define rbBUFFER_UNBLOCK_RX_FLAG ( ( UBaseType_t ) 32 ) to its own variable, to simplify race condition worries.

[SoucheSouche]

The other issue is that this comment is still valid and your current solution won't be accepted.

I am implementing an alternative to your changes using xTaskAbortDelay proposed solution.

[chipweinberger]

@SoucheSouche , did you understand Ivans comment? "Thinking about this again, select on a pair of file descriptors (stdin and eventfd) is probably the cleanest solution." I'm not sure what that solution would look like.

If you use xTaskAbortDelay, make sure the thread is not blocked in user code. 1. suspend the linenoise thread. 2. check its location.

[chipweinberger]

@SoucheSouche another idea - we could send a "enter" key event to vfs buffers to force the thread to exit line noise.

something like:

1. esp_linenoise_quit //prevent any further linenoise stdin reads or command lines being returned
2. usb_serial_jtag_write('\n')

[github-actions[bot]]

	Warnings
:warning:	Some issues found for the commit messages in this PR: the commit message "[Console] fix console deinit: add ability to unblock linenoise, to fix deadlock": summary looks empty type/action looks empty Please fix these commit messages - here are some basic tips: follow Conventional Commits style correct format of commit message should be: <type/action>(<scope/component>): <summary>, for example fix(esp32): Fixed startup timeout issue allowed types are: change,ci,docs,feat,fix,refactor,remove,revert sufficiently descriptive message summary should be between 20 to 72 characters and start with upper case letter avoid Jira references in commit messages (unavailable/irrelevant for our customers) TIP: Install pre-commit hooks and run this check when committing (uses the Conventional Precommit Linter).
:warning:	The source branch "user/chip/console-unblock-try2" incorrect format: contains more than one slash (/). This can cause troubles with git sync. Please rename your branch.

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[SoucheSouche]

Hi @chipweinberger, Sorry that I left this PR not updated for so long. I will get back at it this week. It's been a while so it might take a bit of time to get back into it but I will update you as I go through it. Hopefully we will finally be able to merge it this time.

[SoucheSouche]

Hi @chipweinberger, a little update on the PR. Since it was fairly old, I first had to rebase it on the latest master and realized that your solution was no longer working. The concept of adding 2 states to the console repl is great and works just fine but the solution that you were using to force linenoise to return didn't seem to work.

I experimented with select as @igrr suggested and ended up finding a solution. The very drafty logic implemented in linenoiseDumb() and linenoiseRaw() is the following:

[...]
        if (select(in_fd + 1, &read_fds, NULL, &except_fds, NULL) < 0) {
            // select returned with -1, handle the error
        }

        // std_in is either ready to read or an exceptional condition occurred
        if(FD_ISSET(in_fd, &except_fds)) {
            // exceptional condition occurred, return from linenoise back into the while loop
            // of `esp_console_repl_task` where the repl state will be reevaluated
            break;
        }
        else if(FD_ISSET(in_fd, &read_fds)) {
            // do the reading since std_in is ready for reading
        }
        else {
            continue;
        }

I kept uart_unblock_reads and usb_serial_jtag_unblock_reads and I make them fire an "exceptional condition" event that will make the select return and if(FD_ISSET(in_fd, &except_fds)) evaluated to true.

[chipweinberger]

seems like a reasonable solution!

impressive :) fun :)

[SoucheSouche]

I had to implement the select for the usb serial jtag driver so I will have to first merge this added feature before proceeding with the actual deadlock fix. I will keep you posted.

[chipweinberger]

related: https://github.com/espressif/esp-idf/issues/9964 ([USB Serial JTAG] calling select() & poll() crashes)

[SoucheSouche]

Hi @chipweinberger, a little update on the fix. I am still waiting to merge the select() feature for the usb cdc and usb serial jtag drivers before I can merge the fix for the deadlock. I will let you know when the select() features have been merged but it might take a little while.