Commit a8434ec14 ("MINOR: lists: Implement locked variations.")
introduced locked lists which use the elements pointers as locks
for concurrent operations. A copy-paste typo in LIST_ADDQ_LOCKED()
causes corruption in the list in case the next pointer is already
held, as it restores the previous pointer into the next one. It
may impact the server pools.
This will have to be backported if the commit above is backported.
In LIST_DEL_LOCKED(), initialize p2 to NULL, and only attempt to set it back
to its previous value if we had a previous element, and thus p2 is non-NULL.
Implement LIST_ADD_LOCKED(), LIST_ADDQ_LOCKED(), LIST_DEL_LOCKED() and
LIST_POP_LOCKED().
LIST_ADD_LOCKED, LIST_ADDQ_LOCKED and LIST_DEL_LOCKED work the same as
LIST_ADD, LIST_ADDQ and LIST_DEL, except before any manipulation it locks
the relevant elements of the list, so it's safe to manipulate the list
with multiple threads.
LIST_POP_LOCKED() removes the first element from the list, and returns its
data.
On freebsd, the macro LIST_PREV already exists in the header file
<sys/queue.h>, and this makes a build error.
This patch removes the macros before declaring it. This ensure
that the error doesn't occurs.
Remove the code dealing with the old dual-linked lists imported from
librt that has remained unused for the last 8 years. Now everything
uses the linux-like circular lists instead.
Benoit Dolez reported a failure to start haproxy 1.5-dev19. The
process would immediately report an internal error with missing
fetches from some crap instead of ACL names.
The cause is that some versions of gcc seem to trim static structs
containing a variable array when moving them to BSS, and only keep
the fixed size, which is just a list head for all ACL and sample
fetch keywords. This was confirmed at least with gcc 3.4.6. And we
can't move these structs to const because they contain a list element
which is needed to link all of them together during the parsing.
The bug indeed appeared with 1.5-dev19 because it's the first one
to have some empty ACL keyword lists.
One solution is to impose -fno-zero-initialized-in-bss to everyone
but this is not really nice. Another solution consists in ensuring
the struct is never empty so that it does not move there. The easy
solution consists in having a non-null list head since it's not yet
initialized.
A new "ILH" list head type was thus created for this purpose : create
an Initialized List Head so that gcc cannot move the struct to BSS.
This fixes the issue for this version of gcc and does not create any
burden for the declarations.
This type will be used to maintain back-references to items which
are subject to move between accesses. Typical usage includes session
removal during a listing.
Building ev_kqueue on OpenBSD causes some warnings to occur,
because OpenBSD also uses LIST_* macros in sys/queue.h, included
from sys/event.h. Simply undefine those macros since we don't
need them.
