Add GEC lock mechanism.

Basically re-use the gec lock code from flashrom package.

BUG=chrome-os-partner:12319
TEST=Build and run on link. Only build on snow.
while true; do ectool hello; done &   ; run 10 instances.
                                      ; expect all instances runs okay.

Signed-off-by: Louis Yung-Chieh Lo <yjlou@chromium.org>
Original-Change-Id: I11d5824f46810c6f5a04a564a81387cdea081697
Reviewed-on: https://gerrit.chromium.org/gerrit/29763
Reviewed-by: Randall Spangler <rspangler@chromium.org>
(cherry picked from commit 03d4ed278de2a27a9c2c580ad4d68e30dbcc7630)

Change-Id: Id38ea63e9dc36f13455af5c55f5aeb40571ce00c
Reviewed-on: https://gerrit.chromium.org/gerrit/31092
Reviewed-by: Yung-Chieh Lo <yjlou@chromium.org>
Tested-by: Yung-Chieh Lo <yjlou@chromium.org>

11 files changed, 782 insertions, 4 deletions

diff --git a/Makefile b/Makefile
index 80566276e2..bf96bbe9be 100644
--- a/Makefile
+++ b/Makefile
@@ -37,6 +37,7 @@ include core/$(CORE)/build.mk
 include common/build.mk
 include test/build.mk
 include util/build.mk
+include util/lock/build.mk
 
 includes+=$(includes-y)
 
diff --git a/Makefile.rules b/Makefile.rules
index 27d527f115..98adb101a7 100644
--- a/Makefile.rules
+++ b/Makefile.rules
@@ -119,7 +119,8 @@ $(out)/ec_version.h: $(filter-out $(out)/common/version.o,$(objs))
 $(build-utils): $(out)/%:%.c
 	$(call quiet,c_to_build,BUILDCC)
 
-$(host-utils): $(out)/%:%.c $(foreach u,$(host-util-common),util/$(u).c)
+$(host-utils): $(out)/%:%.c $(foreach u,$(host-util-common),util/$(u).c) \
+			    $(foreach u,$(util-lock-objs),util/lock/$(u).c)
 	$(call quiet,c_to_host,HOSTCC )
 
 $(out)/util/burn_my_ec: $(out)/$(PROJECT).bin
diff --git a/util/ectool.c b/util/ectool.c
index e15bd8a0ec..3acedb0d5c 100644
--- a/util/ectool.c
+++ b/util/ectool.c
@@ -14,6 +14,7 @@
 #include "battery.h"
 #include "comm-host.h"
 #include "lightbar.h"
+#include "lock/gec_lock.h"
 #include "vboot.h"
 
 /* Handy tricks */
@@ -22,6 +23,7 @@
 /* Don't use a macro where an inline will do... */
 static inline int MIN(int a, int b) { return a < b ? a : b; }
 
+#define GEC_LOCK_TIMEOUT_SECS	30  /* 30 secs */
 
 const char help_str[] =
 	"Commands:\n"
@@ -2151,6 +2153,7 @@ const struct command commands[] = {
 int main(int argc, char *argv[])
 {
 	const struct command *cmd;
+	int rv;
 
 	BUILD_ASSERT(ARRAY_SIZE(lb_command_paramcount) == LIGHTBAR_NUM_CMDS);
 	BUILD_ASSERT(ARRAY_SIZE(vb_command_paramcount) == VBOOT_NUM_CMDS);
@@ -2161,17 +2164,28 @@ int main(int argc, char *argv[])
 		return -2;
 	}
 
+	if (acquire_gec_lock(GEC_LOCK_TIMEOUT_SECS) < 0) {
+		fprintf(stderr, "Could not acquire GEC lock.\n");
+		return 1;
+	}
+
 	if (comm_init() < 0)
 		return -3;
 
 	/* Handle commands */
 	for (cmd = commands; cmd->name; cmd++) {
-		if (!strcasecmp(argv[1], cmd->name))
-			return cmd->handler(argc - 1, argv + 1);
+		if (!strcasecmp(argv[1], cmd->name)) {
+			rv = cmd->handler(argc - 1, argv + 1);
+			goto out;
+		}
 	}
 
 	/* If we're still here, command was unknown */
 	fprintf(stderr, "Unknown command '%s'\n\n", argv[1]);
 	print_help(argv[0]);
-	return -2;
+	rv = -2;
+
+out:
+	release_gec_lock();
+	return rv;
 }
diff --git a/util/lock/build.mk b/util/lock/build.mk
new file mode 100644
index 0000000000..1b74bc4cea
--- /dev/null
+++ b/util/lock/build.mk
@@ -0,0 +1,9 @@
+# -*- makefile -*-
+# Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+#
+# Lock library
+#
+
+util-lock-objs=csem ipc_lock gec_lock
diff --git a/util/lock/csem.c b/util/lock/csem.c
new file mode 100644
index 0000000000..a84cbbb2b1
--- /dev/null
+++ b/util/lock/csem.c
@@ -0,0 +1,279 @@
+/*
+ * Copyright 2003 Sun Microsystems, Inc.
+ * Copyright 2010 Google, Inc.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above
+ *    copyright notice, this list of conditions and the following disclaimer
+ *    in the documentation and/or other materials provided with the
+ *    distribution.
+ *  * Neither the name of Google Inc. nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Developer's note: This was open sourced by Sun Microsystems, which got it
+ * via Cobalt Networks.  It has been fairly extensively modified since then.
+ */
+
+#ifndef _GNU_SOURCE
+#  define _GNU_SOURCE 1
+#endif
+#include <sys/types.h>
+#include <sys/ipc.h>
+#include <sys/sem.h>
+#include <sys/stat.h>
+#include <time.h>
+#include <errno.h>
+#include <sched.h>
+
+#include "csem.h"
+
+#if defined(__GNU_LIBRARY__) && !defined(_SEM_SEMUN_UNDEFINED)
+/* union semun is defined by including <sys/sem.h> */
+#else
+/* according to X/OPEN we have to define it ourselves */
+union semun {
+	int val;                    /* value for SETVAL */
+	struct semid_ds *buf;       /* buffer for IPC_STAT, IPC_SET */
+	unsigned short int *array;  /* array for GETALL, SETALL */
+	struct seminfo *__buf;      /* buffer for IPC_INFO */
+};
+#endif
+
+/*
+ * On some platforms semctl(SETVAL) sets sem_otime, on other platforms it
+ * does not.  Figure out what this platform does.
+ *
+ * Returns 0 if semctl(SETVAL) does not set sem_otime
+ * Returns 1 if semctl(SETVAL) does set sem_otime
+ * Returns -1 on error
+ */
+static int does_semctl_set_otime(void)
+{
+	int sem_id;
+	int ret;
+
+	/* create a test semaphore */
+	sem_id = semget(IPC_PRIVATE, 1, S_IRUSR|S_IWUSR);
+	if (sem_id < 0) {
+		return -1;
+	}
+
+	/* set the value */
+	if (csem_setval(sem_id, 1) < 0) {
+		csem_destroy(sem_id);
+		return -1;
+	}
+
+	/* read sem_otime */
+	ret = (csem_get_otime(sem_id) > 0) ? 1 : 0;
+
+	/* clean up */
+	csem_destroy(sem_id);
+
+	return ret;
+}
+
+int csem_create(key_t key, unsigned val)
+{
+	static int need_otime_hack = -1;
+	int sem_id;
+
+	/* see if we need to trigger a semop to set sem_otime */
+	if (need_otime_hack < 0) {
+		int ret = does_semctl_set_otime();
+		if (ret < 0) {
+			return -1;
+		}
+		need_otime_hack = !ret;
+	}
+
+	/* create it or fail */
+	sem_id = semget(key, 1, IPC_CREAT|IPC_EXCL | S_IRUSR|S_IWUSR);
+	if (sem_id < 0) {
+		return -1;
+	}
+
+	/* initalize the value */
+	if (need_otime_hack) {
+		val++;
+	}
+	if (csem_setval(sem_id, val) < 0) {
+		csem_destroy(sem_id);
+		return -1;
+	}
+
+	if (need_otime_hack) {
+		/* force sem_otime to change */
+		csem_down(sem_id);
+	}
+
+	return sem_id;
+}
+
+/* how many times to loop, waiting for sem_otime */
+#define MAX_OTIME_LOOPS 1000
+
+int csem_get(key_t key)
+{
+	int sem_id;
+	int i;
+
+	/* CSEM_PRIVATE needs to go through csem_create() to get an
+	 * initial value */
+	if (key == CSEM_PRIVATE) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	/* get the (assumed existing) semaphore */
+	sem_id = semget(key, 1, S_IRUSR|S_IWUSR);
+	if (sem_id < 0) {
+		return -1;
+	}
+
+	/* loop until sem_otime != 0, which means it has been initialized */
+	for (i = 0; i < MAX_OTIME_LOOPS; i++) {
+		time_t otime = csem_get_otime(sem_id);
+		if (otime < 0) {
+			/* error */
+			return -1;
+		}
+		if (otime > 0) {
+			/* success */
+			return sem_id;
+		}
+		/* retry */
+		sched_yield();
+	}
+
+	/* fell through - error */
+	return -1;
+}
+
+int csem_get_or_create(key_t key, unsigned val)
+{
+	int sem_id;
+
+	/* try to create the semaphore */
+	sem_id = csem_create(key, val);
+	if (sem_id >= 0 || errno != EEXIST) {
+		/* it either succeeded or got an error */
+		return sem_id;
+	}
+
+	/* it must exist already - get it */
+	sem_id = csem_get(key);
+	if (sem_id < 0) {
+		return -1;
+	}
+
+	return sem_id;
+}
+
+int csem_destroy(int sem_id)
+{
+	return semctl(sem_id, 0, IPC_RMID);
+}
+
+int csem_getval(int sem_id)
+{
+	return semctl(sem_id, 0, GETVAL);
+}
+
+int csem_setval(int sem_id, unsigned val)
+{
+	union semun arg;
+	arg.val = val;
+	if (semctl(sem_id, 0, SETVAL, arg) < 0) {
+		return -1;
+	}
+	return 0;
+}
+
+static int csem_up_undoflag(int sem_id, int undoflag)
+{
+	struct sembuf sops;
+	sops.sem_num = 0;
+	sops.sem_op = 1;
+	sops.sem_flg = undoflag;
+	return semop(sem_id, &sops, 1);
+}
+
+int csem_up(int sem_id)
+{
+	return csem_up_undoflag(sem_id, 0);
+}
+
+int csem_up_undo(int sem_id)
+{
+	return csem_up_undoflag(sem_id, SEM_UNDO);
+}
+
+static int csem_down_undoflag(int sem_id, int undoflag)
+{
+	struct sembuf sops;
+	sops.sem_num = 0;
+	sops.sem_op = -1;
+	sops.sem_flg = undoflag;
+	return semop(sem_id, &sops, 1);
+}
+
+int csem_down(int sem_id)
+{
+	return csem_down_undoflag(sem_id, 0);
+}
+
+int csem_down_undo(int sem_id)
+{
+	return csem_down_undoflag(sem_id, SEM_UNDO);
+}
+
+static int csem_down_timeout_undoflag(int sem_id,
+                                      struct timespec *timeout,
+                                      int undoflag)
+{
+	struct sembuf sops;
+	sops.sem_num = 0;
+	sops.sem_op = -1;
+	sops.sem_flg = undoflag;
+	return semtimedop(sem_id, &sops, 1, timeout);
+}
+
+int csem_down_timeout(int sem_id, struct timespec *timeout)
+{
+	return csem_down_timeout_undoflag(sem_id, timeout, 0);
+}
+
+int csem_down_timeout_undo(int sem_id, struct timespec *timeout)
+{
+	return csem_down_timeout_undoflag(sem_id, timeout, SEM_UNDO);
+}
+
+time_t csem_get_otime(int sem_id)
+{
+	union semun arg;
+	struct semid_ds ds;
+	arg.buf = &ds;
+	if (semctl(sem_id, 0, IPC_STAT, arg) < 0) {
+		return -1;
+	}
+	return ds.sem_otime;
+}
diff --git a/util/lock/csem.h b/util/lock/csem.h
new file mode 100644
index 0000000000..10a5c5ff94
--- /dev/null
+++ b/util/lock/csem.h
@@ -0,0 +1,154 @@
+/*
+ * Copyright 2003 Sun Microsystems, Inc.
+ * Copyright 2010 Google, Inc.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above
+ *    copyright notice, this list of conditions and the following disclaimer
+ *    in the documentation and/or other materials provided with the
+ *    distribution.
+ *  * Neither the name of Google Inc. nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Developer's note: This was open sourced by Sun Microsystems, which got it
+ * via Cobalt Networks.  It has been fairly extensively modified since then.
+ */
+
+#ifndef CSEM_H__
+#define CSEM_H__
+
+#include <sys/ipc.h>
+#include <time.h>
+
+/* create a private key */
+#define CSEM_PRIVATE IPC_PRIVATE
+
+/*
+ * Create a new semaphore with the specified key, initialized to the
+ * specified value.  If the key is CSEM_PRIVATE, a new private semaphore
+ * is allocated.
+ *
+ * Returns the sempahore ID (>= 0) on success.
+ * Returns < 0 on error, or if the key already exists.
+ */
+extern int csem_create(key_t key, unsigned val);
+
+/*
+ * Fetch an existing semaphore with the specified key.
+ *
+ * Returns the sempahore ID (>= 0) on success.
+ * Returns < 0 on error, or if the key does not exist.
+ */
+extern int csem_get(key_t key);
+
+/*
+ * Fetch or create a semaphore with the specified key.  If the semaphore
+ * did not exist, it will be created with the specified value.
+ *
+ * Returns the sempahore ID (>= 0) on success.
+ * Returns < 0 on error.
+ */
+extern int csem_get_or_create(key_t key, unsigned val);
+
+/*
+ * Destroy the semaphore.
+ *
+ * Returns 0 on success.
+ * Returns < 0 on error.
+ */
+extern int csem_destroy(int sem_id);
+
+/*
+ * Get the value of the semaphore.
+ *
+ * Returns the value (>= 0) on success.
+ * Returns < 0 on error.
+ */
+extern int csem_getval(int sem_id);
+
+/*
+ * Set the value of the semaphore.
+ *
+ * Returns 0 on success.
+ * Returns < 0 on error.
+ */
+extern int csem_setval(int sem_id, unsigned val);
+
+/*
+ * Increment the semaphore.
+ *
+ * Returns 0 on success.
+ * Returns < 0 on error.
+ */
+extern int csem_up(int sem_id);
+
+/*
+ * Increment the semaphore.  This operation will be undone when the
+ * process terminates.
+ *
+ * Returns 0 on success.
+ * Returns < 0 on error.
+ */
+extern int csem_up_undo(int sem_id);
+
+/*
+ * Decrement the semaphore, or block if sem == 0.
+ *
+ * Returns 0 on success.
+ * Returns < 0 on error.
+ */
+extern int csem_down(int sem_id);
+
+/*
+ * Decrement the semaphore, or block if sem == 0.  This operation will be
+ * undone when the process terminates.
+ *
+ * Returns 0 on success.
+ * Returns < 0 on error.
+ */
+extern int csem_down_undo(int sem_id);
+
+/*
+ * Decrement the semaphore, or block with a timeout if sem == 0.
+ *
+ * Returns 0 on success.
+ * Returns < 0 on error.
+ */
+extern int csem_down_timeout(int sem_id, struct timespec *timeout);
+
+/*
+ * Decrement the semaphore, or block with a timeout if sem == 0.  This
+ * operation will be undone when the process terminates.
+ *
+ * Returns 0 on success.
+ * Returns < 0 on error.
+ */
+extern int csem_down_timeout_undo(int sem_id, struct timespec *timeout);
+
+/*
+ * Get the timestamp of the last csem_up()/csem_down() call.
+ *
+ * Returns sem_otime on success.
+ * Returns < 0 on error
+ */
+extern time_t csem_get_otime(int sem_id);
+
+#endif /* CSEM_H__ */
diff --git a/util/lock/gec_lock.c b/util/lock/gec_lock.c
new file mode 100644
index 0000000000..4df231af3e
--- /dev/null
+++ b/util/lock/gec_lock.c
@@ -0,0 +1,45 @@
+/* Copyright 2012, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *    * Redistributions of source code must retain the above copyright
+ *      notice, this list of conditions and the following disclaimer.
+ *    * Redistributions in binary form must reproduce the above
+ *      copyright notice, this list of conditions and the following
+ *      disclaimer in the documentation and/or other materials provided
+ *      with the distribution.
+ *    * Neither the name of Google Inc. nor the names of its
+ *      contributors may be used to endorse or promote products derived
+ *      from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "gec_lock.h"
+#include "ipc_lock.h"
+#include "locks.h"
+
+static struct ipc_lock gec_lock = IPC_LOCK_INIT(GECLOCK);
+
+int acquire_gec_lock(int timeout_secs)
+{
+	return acquire_lock(&gec_lock, timeout_secs * 1000);
+}
+
+int release_gec_lock(void)
+{
+	return release_lock(&gec_lock);
+}
diff --git a/util/lock/gec_lock.h b/util/lock/gec_lock.h
new file mode 100644
index 0000000000..13b0f9d92c
--- /dev/null
+++ b/util/lock/gec_lock.h
@@ -0,0 +1,51 @@
+/* Copyright 2012, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *    * Redistributions of source code must retain the above copyright
+ *      notice, this list of conditions and the following disclaimer.
+ *    * Redistributions in binary form must reproduce the above
+ *      copyright notice, this list of conditions and the following
+ *      disclaimer in the documentation and/or other materials provided
+ *      with the distribution.
+ *    * Neither the name of Google Inc. nor the names of its
+ *      contributors may be used to endorse or promote products derived
+ *      from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef GEC_LOCK_H__
+#define GEC_LOCK_H__
+
+/*
+ * acquire_gec_lock  -  acquire global lock
+ *
+ * returns 0 to indicate lock acquired
+ * returns >0 to indicate lock was already held
+ * returns <0 to indicate failed to acquire lock
+ */
+extern int acquire_gec_lock(int timeout_secs);
+
+/*
+ * release_gec_lock  -  release global lock
+ *
+ * returns 0 if lock was released successfully
+ * returns -1 if lock had not been held before the call
+ */
+extern int release_gec_lock(void);
+
+#endif /* GEC_LOCK_H__ */
diff --git a/util/lock/ipc_lock.c b/util/lock/ipc_lock.c
new file mode 100644
index 0000000000..5bc816c894
--- /dev/null
+++ b/util/lock/ipc_lock.c
@@ -0,0 +1,106 @@
+/* Copyright 2012, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *    * Redistributions of source code must retain the above copyright
+ *      notice, this list of conditions and the following disclaimer.
+ *    * Redistributions in binary form must reproduce the above
+ *      copyright notice, this list of conditions and the following
+ *      disclaimer in the documentation and/or other materials provided
+ *      with the distribution.
+ *    * Neither the name of Google Inc. nor the names of its
+ *      contributors may be used to endorse or promote products derived
+ *      from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <inttypes.h>
+#include <stdio.h>
+#include <time.h>
+
+#include "csem.h"
+#include "ipc_lock.h"
+
+static int lock_init(struct ipc_lock *lock)
+{
+	if (lock->sem < 0) {
+		/* get or create the semaphore, init to 1 if needed */
+		int sem = csem_get_or_create(lock->key, 1);
+		if (sem < 0) {
+			return -1;
+		}
+		lock->sem = sem;
+	}
+	return 0;
+}
+
+static void msecs_to_timespec(int msecs, struct timespec *tmspec)
+{
+	tmspec->tv_sec = msecs / 1000;
+	tmspec->tv_nsec = (msecs % 1000) * 1000 * 1000;
+}
+
+int acquire_lock(struct ipc_lock *lock, int timeout_msecs)
+{
+	int ret;
+	struct timespec timeout;
+	struct timespec *timeout_ptr;
+
+	/* initialize the lock */
+	if (lock_init(lock) < 0) {
+		fprintf(stderr, "%s(): failed to init lock 0x%08x\n",
+		        __func__, (uint32_t)lock->key);
+		return -1;
+	}
+
+	/* check if it is already held */
+	if (lock->is_held) {
+		return 1;
+	}
+
+	/* calculate the timeout */
+	if (timeout_msecs >= 0) {
+		timeout_ptr = &timeout;
+		msecs_to_timespec(timeout_msecs, timeout_ptr);
+	} else {
+		timeout_ptr = NULL;
+	}
+
+	/* try to get the lock */
+	ret = csem_down_timeout_undo(lock->sem, timeout_ptr);
+	if (ret < 0) {
+		fprintf(stderr, "%s(): failed to acquire lock 0x%08x\n",
+		        __func__, (uint32_t)lock->key);
+		return -1;
+	}
+
+	/* success */
+	lock->is_held = 1;
+	return 0;
+}
+
+int release_lock(struct ipc_lock *lock)
+{
+	if (lock->is_held) {
+		lock->is_held = 0;
+		csem_up_undo(lock->sem);
+		/* NOTE: do not destroy the semaphore, we want it to persist */
+		return 0;
+	}
+        /* did not hold the lock */
+        return -1;
+}
diff --git a/util/lock/ipc_lock.h b/util/lock/ipc_lock.h
new file mode 100644
index 0000000000..b85de286b7
--- /dev/null
+++ b/util/lock/ipc_lock.h
@@ -0,0 +1,71 @@
+/* Copyright 2012, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *    * Redistributions of source code must retain the above copyright
+ *      notice, this list of conditions and the following disclaimer.
+ *    * Redistributions in binary form must reproduce the above
+ *      copyright notice, this list of conditions and the following
+ *      disclaimer in the documentation and/or other materials provided
+ *      with the distribution.
+ *    * Neither the name of Google Inc. nor the names of its
+ *      contributors may be used to endorse or promote products derived
+ *      from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef IPC_LOCK_H__
+#define IPC_LOCK_H__
+
+#include <sys/ipc.h>
+
+struct ipc_lock {
+	key_t key;         /* provided by the developer */
+	int sem;           /* internal */
+	int is_held;       /* internal */
+};
+
+/* don't use C99 initializers here, so this can be used in C++ code */
+#define IPC_LOCK_INIT(key) \
+	{ \
+		key,       /* name */ \
+		-1,        /* sem */ \
+		0,         /* is_held */ \
+	}
+
+/*
+ * acquire_lock: acquire a lock
+ *
+ * timeout <0 = no timeout (try forever)
+ * timeout 0  = do not wait (return immediately)
+ * timeout >0 = wait up to $timeout milliseconds (subject to kernel scheduling)
+ *
+ * return 0   = lock acquired
+ * return >0  = lock was already held
+ * return <0  = failed to acquire lock
+ */
+extern int acquire_lock(struct ipc_lock *lock, int timeout_msecs);
+
+/*
+ * release_lock: release a lock
+ *
+ * returns 0 if lock was released successfully
+ * returns -1 if lock had not been held before the call
+ */
+extern int release_lock(struct ipc_lock *lock);
+
+#endif /* IPC_LOCK_H__ */
diff --git a/util/lock/locks.h b/util/lock/locks.h
new file mode 100644
index 0000000000..39dfc933f3
--- /dev/null
+++ b/util/lock/locks.h
@@ -0,0 +1,47 @@
+/* Copyright 2012, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *    * Redistributions of source code must retain the above copyright
+ *      notice, this list of conditions and the following disclaimer.
+ *    * Redistributions in binary form must reproduce the above
+ *      copyright notice, this list of conditions and the following
+ *      disclaimer in the documentation and/or other materials provided
+ *      with the distribution.
+ *    * Neither the name of Google Inc. nor the names of its
+ *      contributors may be used to endorse or promote products derived
+ *      from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef LOCKS_H__
+#define LOCKS_H__
+
+/* this is the base key, since we have to pick something global */
+#define IPC_LOCK_KEY	(0x67736c00 & 0xfffffc00) /* 22 bits "gsl" */
+
+/* The ordering of the following keys matters a lot. We don't want to reorder
+ * keys and have a new binary dependent on deployed/used because it will break
+ * atomicity of existing users and binaries. In other words, DO NOT REORDER. */
+
+/* this is the "big lock". */
+#define BIGLOCK		(IPC_LOCK_KEY + 0)
+
+/* for Google EC */
+#define GECLOCK		(IPC_LOCK_KEY + 1)
+
+#endif /* LOCKS_H__ */