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/*--------------------------------------------------------------------*/
/*--- Semaphore stuff. sema.c ---*/
/*--------------------------------------------------------------------*/
/*
This file is part of Valgrind, a dynamic binary instrumentation
framework.
Copyright (C) 2000-2017 Julian Seward
jseward@acm.org
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, see <http://www.gnu.org/licenses/>.
The GNU General Public License is contained in the file COPYING.
*/
#include "pub_core_basics.h"
#include "pub_core_debuglog.h"
#include "pub_core_vki.h"
#include "pub_core_libcassert.h"
#include "pub_core_libcfile.h"
#include "pub_core_libcproc.h" // For VG_(gettid)()
#include "pub_core_inner.h"
#if defined(ENABLE_INNER_CLIENT_REQUEST)
#include "helgrind/helgrind.h"
#endif
#include "priv_sema.h"
/*
Slower (than the removed futex-based sema scheme) but more portable
pipe-based token passing scheme.
*/
/* Cycle the char passed through the pipe through 'A' .. 'Z' to make
it easier to make sense of strace/truss output - makes it possible
to see more clearly the change of ownership of the lock. Need to
be careful to reinitialise it at fork() time. */
static HChar sema_char = '!'; /* will cause assertion failures if used
before sema_init */
void ML_(sema_init)(vg_sema_t *sema)
{
HChar buf[2];
Int res, r;
r = VG_(pipe)(sema->pipe);
vg_assert(r == 0);
vg_assert(sema->pipe[0] != sema->pipe[1]);
sema->pipe[0] = VG_(safe_fd)(sema->pipe[0]);
sema->pipe[1] = VG_(safe_fd)(sema->pipe[1]);
if (0)
VG_(debugLog)(0,"zz","sema_init: %d %d\n", sema->pipe[0],
sema->pipe[1]);
vg_assert(sema->pipe[0] != sema->pipe[1]);
sema->owner_lwpid = -1;
/* create initial token */
sema_char = 'A';
buf[0] = sema_char;
buf[1] = 0;
sema_char++;
INNER_REQUEST(ANNOTATE_RWLOCK_CREATE(sema));
INNER_REQUEST(ANNOTATE_BENIGN_RACE_SIZED(&sema->owner_lwpid,
sizeof(sema->owner_lwpid), ""));
res = VG_(write)(sema->pipe[1], buf, 1);
vg_assert(res == 1);
}
void ML_(sema_deinit)(vg_sema_t *sema)
{
vg_assert(sema->owner_lwpid != -1); /* must be initialised */
vg_assert(sema->pipe[0] != sema->pipe[1]);
INNER_REQUEST(ANNOTATE_RWLOCK_DESTROY(sema));
VG_(close)(sema->pipe[0]);
VG_(close)(sema->pipe[1]);
sema->pipe[0] = sema->pipe[1] = -1;
sema->owner_lwpid = -1;
}
/* get a token */
void ML_(sema_down)( vg_sema_t *sema, Bool as_LL )
{
HChar buf[2];
Int ret;
Int lwpid = VG_(gettid)();
vg_assert(sema->owner_lwpid != lwpid); /* can't have it already */
vg_assert(sema->pipe[0] != sema->pipe[1]);
again:
buf[0] = buf[1] = 0;
ret = VG_(read)(sema->pipe[0], buf, 1);
INNER_REQUEST(ANNOTATE_RWLOCK_ACQUIRED(sema, /*is_w*/1));
if (ret != 1)
VG_(debugLog)(1, "scheduler",
"ML_(sema_down): read returned %d\n", ret);
if (ret == -VKI_EINTR)
goto again;
vg_assert(ret == 1); /* should get exactly 1 token */
vg_assert(buf[0] >= 'A' && buf[0] <= 'Z');
vg_assert(buf[1] == 0);
if (sema_char == 'Z') sema_char = 'A'; else sema_char++;
sema->owner_lwpid = lwpid;
sema->held_as_LL = as_LL;
}
/* put token back */
void ML_(sema_up)( vg_sema_t *sema, Bool as_LL )
{
Int ret;
HChar buf[2];
vg_assert(as_LL == sema->held_as_LL);
buf[0] = sema_char;
buf[1] = 0;
vg_assert(sema->owner_lwpid != -1); /* must be initialised */
vg_assert(sema->pipe[0] != sema->pipe[1]);
vg_assert(sema->owner_lwpid == VG_(gettid)()); /* must have it */
sema->owner_lwpid = 0;
INNER_REQUEST(ANNOTATE_RWLOCK_RELEASED(sema, /*is_w*/1));
ret = VG_(write)(sema->pipe[1], buf, 1);
if (ret != 1)
VG_(debugLog)(0, "scheduler",
"VG_(sema_up):write returned %d\n", ret);
vg_assert(ret == 1);
}
/*--------------------------------------------------------------------*/
/*--- end ---*/
/*--------------------------------------------------------------------*/
|
