Re: Dereference before NULL check (src/backend/storage/ipc/latch.c) - Mailing list pgsql-hackers

From Ranier Vilela
Subject Re: Dereference before NULL check (src/backend/storage/ipc/latch.c)
Date
Msg-id CAEudQAqkgqpw7fYRod_RzK5jLSY4SW7aPF_UWXQKueNV+gOy4g@mail.gmail.com
Whole thread Raw
In response to Re: Dereference before NULL check (src/backend/storage/ipc/latch.c)  (Kyotaro Horiguchi <horikyota.ntt@gmail.com>)
Responses Re: Dereference before NULL check (src/backend/storage/ipc/latch.c)
List pgsql-hackers
Em ter., 3 de nov. de 2020 às 22:09, Kyotaro Horiguchi <horikyota.ntt@gmail.com> escreveu:
At Tue, 3 Nov 2020 20:44:23 +1300, Thomas Munro <thomas.munro@gmail.com> wrote in
> On Tue, Nov 3, 2020 at 12:50 AM Kyotaro Horiguchi
> <horikyota.ntt@gmail.com> wrote:
> > With the fix patch, it changes to:
> >
> > [16632] LOG:  FALSE LATCH: 0000000000000000
>
> Nice repo.  But is it OK to not reset the Win32 event in this case?
> Does it still work correctly if you wait on the latch after that
> happened, and perhaps after the PG latch is reset?

I'm not sure what is the point of the question, but the previous patch
doesn't omit resetting the Win32-event in that case.  In the same way
with other implements of the same function, it resets the trigger that
woke up the process since the trigger is no longer needed even if we
are not waiting on it.

If we call WaitLatch(OrSocket) that waits on the latch, it immediately
returns because the latch is set. If we called ResetLatch before the
next call to WaitLatch(), it correctly waits on a trigger to be
pulled.
+1
The patch for me is syntactically equal to the code changed and
avoids the dereference.

regards,
Ranier Vilela

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