Re: Possible problem with shm_mq spin lock

Haribabu Kommi <kommi(dot)haribabu(at)gmail(dot)com> writes:
> Thanks for the details. I am sorry It is not proc_exit. It is the exit
> callback functions that can cause problem.

> The following is the callstack where the problem can happen, if the signal
> handler is called after the spin lock took by the worker.

> Breakpoint 1, 0x000000000072dd83 in shm_mq_detach ()
> (gdb) bt
> #0 0x000000000072dd83 in shm_mq_detach ()
> #1 0x000000000072e7db in shm_mq_detach_callback ()
> #2 0x0000000000726d71 in dsm_detach ()
> #3 0x0000000000726c43 in dsm_backend_shutdown ()
> #4 0x0000000000727450 in shmem_exit ()
> #5 0x00000000007272fc in proc_exit_prepare ()
> #6 0x0000000000727501 in atexit_callback ()
> #7 0x00000030ff435da2 in exit () from /lib64/libc.so.6
> #8 0x00000000006ddaec in bgworker_quickdie ()

Or in other words, Robert broke it. This control path should absolutely
not occur: the entire point of the on_exit_reset call in quickdie() is to
prevent any callbacks from being executed when we get to shmem_exit().
DSM-related functions DO NOT get an exemption.

regards, tom lane