From 0955fa72f5f45e93e5d1919bfb0d0b1f5c93e7f2 Mon Sep 17 00:00:00 2001
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Sat, 5 Jun 2021 23:15:14 +0200
Subject: global: replace rwlock with mtx if never rlocked

There were multiple places where a rwlock was used despite never
rlocking, so just change these into mtxs. This was done with the aid of
Coccinelle's spatch, using this input:

    #spatch -j 4 --recursive-includes --include-headers-for-types --include-headers --in-place --macro-file <seebelow.h>

    virtual after_start

    @initialize:ocaml@
    @@

    let has_write_table = Hashtbl.create 101
    let has_read_table = Hashtbl.create 101

    let ok i m =
      let entry = (i,m) in
      Hashtbl.mem has_write_table entry && not(Hashtbl.mem has_read_table entry)

    @hasw depends on !after_start@
    identifier i,m;
    struct i x;
    @@

    (
    rw_wlock(&x.m)
    |
    rw_wunlock(&x.m)
    )

    @script:ocaml@
    i << hasw.i;
    m << hasw.m;
    @@
    Hashtbl.replace has_write_table (i,m) ()

    @hasr depends on !after_start@
    identifier i,m;
    struct i x;
    @@

    (
    rw_rlock(&x.m)
    |
    rw_runlock(&x.m)
    )

    @script:ocaml@
    i << hasr.i;
    m << hasr.m;
    @@
    Hashtbl.replace has_read_table (i,m) ()

    @finalize:ocaml depends on !after_start@
    wt << merge.has_write_table;
    rt << merge.has_read_table;
    @@

    let redo ts dst =
      List.iter (Hashtbl.iter (fun k _ -> Hashtbl.add dst k ())) ts in
    redo wt has_write_table;
    redo rt has_read_table;

    let it = new iteration() in
    it#add_virtual_rule After_start;
    it#register()

    (* ----------------------------------------------------------- *)

    @depends on after_start@
    identifier i;
    identifier m : script:ocaml(i) { ok i m };
    @@

    struct i {
      ...
    - struct rwlock m;
    + struct mtx m;
      ...
    }

    @depends on after_start disable fld_to_ptr@
    identifier m;
    identifier i : script:ocaml(m) { ok i m };
    struct i x;
    @@

    - rw_wlock
    + mtx_lock
       (&x.m)

    @depends on after_start disable fld_to_ptr@
    identifier m;
    identifier i : script:ocaml(m) { ok i m };
    struct i x;
    @@

    - rw_wunlock
    + mtx_unlock
       (&x.m)

    @depends on after_start disable fld_to_ptr@
    identifier m;
    expression e;
    identifier i : script:ocaml(m) { ok i m };
    struct i x;
    @@

    - rw_init(&x.m, e);
    + mtx_init(&x.m, e, NULL, MTX_DEF);

    @depends on after_start disable fld_to_ptr@
    identifier m;
    identifier i : script:ocaml(m) { ok i m };
    struct i x;
    @@

    - rw_destroy
    + mtx_destroy
       (&x.m)

    @depends on after_start disable fld_to_ptr, ptr_to_array@
    identifier m;
    identifier i : script:ocaml(m) { ok i m };
    struct i *x;
    @@

    - rw_wlock
    + mtx_lock
       (&x->m)

    @depends on after_start disable fld_to_ptr, ptr_to_array@
    identifier m;
    identifier i : script:ocaml(m) { ok i m };
    struct i *x;
    @@

    - rw_wunlock
    + mtx_unlock
       (&x->m)

    @depends on after_start disable fld_to_ptr, ptr_to_array@
    identifier m;
    expression e;
    identifier i : script:ocaml(m) { ok i m };
    struct i *x;
    @@

    - rw_init(&x->m, e);
    + mtx_init(&x->m, e, NULL, MTX_DEF);

    @depends on after_start disable fld_to_ptr, ptr_to_array@
    identifier m;
    identifier i : script:ocaml(m) { ok i m };
    struct i *x;
    @@

    - rw_destroy
    + mtx_destroy
       (&x->m)

A few macros needed to be provided manually for the parser to work:

    #define LIST_HEAD(x,y) int
    #define TAILQ_HEAD(x,y) int
    #define STAILQ_HEAD(x,y) int
    #define CK_LIST_HEAD(x,y) int
    #define CK_LIST_ENTRY(x) int
    #define LIST_ENTRY(x) int
    #define TAILQ_ENTRY(x) int
    #define STAILQ_ENTRY(x) int

Co-authored-by: Julia Lawall <julia.lawall@inria.fr>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 TODO.md | 1 -
 1 file changed, 1 deletion(-)

(limited to 'TODO.md')

diff --git a/TODO.md b/TODO.md
index 99a4cbe..3a05550 100644
--- a/TODO.md
+++ b/TODO.md
@@ -10,7 +10,6 @@
 - Review all included headers, and minimize a bit.
 - Figure out clear locking rules for network stack stuff -- when different
   functions run under what locks and what they race with.
-- There are a few rwlocks that only ever wlock. Make these mtx instead.
 
 ### Crypto TODO
 
-- 
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