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Re: [lwip-users] Do functions like sys_mbox_invalid() need to be thread

From: Grant Edwards
Subject: Re: [lwip-users] Do functions like sys_mbox_invalid() need to be thread safe?
Date: Wed, 10 Nov 2021 21:34:19 -0000 (UTC)
User-agent: slrn/1.0.3 (Linux)

On 2021-11-10, goldsimon@gmx.de <goldsimon@gmx.de> wrote:
>> I mean can two invocations of the sys_* (mailbox, mutex or semaphore)
>> functions happen "at the same time".  For example: can the execution
>> of one call to sys_{sem,mutex,mbox}_set_invalid() be interrupted or
>> suspended by another call to that same function? [The second
>> invocation would be for a different object obviously.] After the second
>> invocation finished, the first one would then resume.
> Yes, ok, that can of course happen.

I thought so. The original authors of the port clearly did not, even
though they seemed aware of the possiblity of some other functions
being called re-entrantly.

> There's no restriction between calling those functions on different
> objects.

OK, thanks — I've definitely got race conditions I need to fix. :)

> The only guarantee you get with lwIP is probably that allocation and
> deallocation points are safe...

I don't quite understand: what does "points are safe" mean?

Thanks again,


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