Gregory Stark wrote:
> "Gregory Stark" <[EMAIL PROTECTED]> writes:
>> "Gregory Stark" <[EMAIL PROTECTED]> writes:
>>> "Tom Lane" <[EMAIL PROTECTED]> writes:
>>>> Gregory Stark <[EMAIL PROTECTED]> writes:
>>>>> We're seeing a problem where occasionally a process appears to be granted 
>>>>> a
>>>>> lock but miss its semaphore signal.
>>>> Kernel bug maybe?  What's the platform?
> I've written a synthetic test program to check for lost semaphore wakeups. I
> can't seem to produce any on my machine but haven't had a chance to run it yet
> on the benchmark machine that's been showing the problem.
> If I can't produce any lost wakeups with a program like this it looks more
> like it might be a Postgres or GCC bug than a Linux bug.
> It would be helpful if people could run this on various architectures and
> various versions of Linux (or other OSes). I've been running it with 40
> processes for an hour, but even shorter runs would be useful. It will drive
> the load on your machine through the roof but doesn't cause any i/o.

doesn't work on OpenBSD:

$ gcc -o ipctest ipctest.c -lpthread
$ ./ipctest 40 3600
running with 40 processes for 3600s
sem_init: Operation not permitted

"This implementation does not support shared semaphores, and reports
this fact by setting errno to EPERM.  This is perhaps a stretch of the
intention of POSIX, but is compliant, with the caveat that sem_init()
always reports a permissions error when an attempt to create a shared
semaphore is made."


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