[lwip-devel] [bug #19167] tcp timeout handler can cause crash being invoked by sys_sem_wait()

[Andreas Becker]

Follow-up Comment #10, bug #19167 (project lwip):

Hi Dimitry, 

not bad, a real good analysis.

Comment 8: My fault, I thought there is a problem to execute a timeout in
history. But there is no problem. So I do not prefere the old timeout
handling.

Timer overflow: Is wraping around the maximum a problem in other systems? If
this is a Problem we both going into trouble. Your expire code will also work
with 16bit integer, but than the longest timeout is less than an hour.

Timefeeling: The problem in the older solutions is, that we have an jitter in
execution time. All Timers are allways executed to late and the error of the
absolute execution time grows. Between two execution times it is constant.
Both of our solutions will handle this. So this behavior will be removed.

Comment 9: Inserting a new timeout handler has to be calculated from
timeouts->remember. So this schould work more correct.

Timeroverflow 2: I know why it is better, to use old timeout handling (time-
differences) than expired time. My solution does not realy count on a correct
systimer-wrapp. I use the type sys_arch_timestamp_t as an system depended
timeout and then only use the macro SYS_ARCH_TIMESTAMP_DIFF as an
implementatin specific (function) to calculate the time difference of two
sys_arch_timestamp_t's. It is not my problem, if the specific implementations
uses an 24bit timestamp. I only want to know the difference.

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