/usr/src/blcr-0.8.5/libcr/cr_cs.c is in blcr-dkms 0.8.5-2.1.
This file is owned by root:root, with mode 0o644.
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* Berkeley Lab Checkpoint/Restart (BLCR) for Linux is Copyright (c)
* 2008, The Regents of the University of California, through Lawrence
* Berkeley National Laboratory (subject to receipt of any required
* approvals from the U.S. Dept. of Energy). All rights reserved.
*
* Portions may be copyrighted by others, as may be noted in specific
* copyright notices within specific files.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library 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
* Library General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
* $Id: cr_cs.c,v 1.67.14.3 2011/08/24 02:35:39 phargrov Exp $
*/
#include <errno.h>
#include "cr_private.h"
//
// Private data
//
#define CRI_CONTEXT_MASK (CR_THREAD_CONTEXT | CR_SIGNAL_CONTEXT)
//
// Private functions
//
static inline void
poll_checkpoint(cri_info_t *info)
{
if (cri_atomic_dec_and_test(&info->cr_cs_count)) {
cri_black_lock(&cri_cs_lock);
cri_start_checkpoint(info);
cri_black_unlock(&cri_cs_lock);
}
}
// signal_handler()
//
// Signal handler for threads w/ signal-context handlers
static void
my_handler(int signr, siginfo_t *siginfo, void *context)
{
int saved_errno = errno;
cri_info_t *info = cri_info_location(); // thread-specific
cri_checkpoint_info_init(info);
if (cri_cmp_swap(&info->cr_state, CR_STATE_IDLE, CR_STATE_PENDING)) {
cri_atomic_inc(&cri_live_count);
poll_checkpoint(info);
}
errno = saved_errno;
}
static int
do_state(cri_info_t *info)
{
int state = cri_atomic_read(&info->cr_state);
if ((state == CR_STATE_IDLE) && cri_atomic_read(&cri_live_count)) {
state = CR_STATE_PENDING;
}
return state;
}
// This mess is to prevent starvation by not entering an
// outermost critical section when a checkpoint is pending
// or running in ANY thread.
static int
try_enter(cri_info_t *info) {
cri_atomic_t *count = &info->cr_cs_count;
int old;
// First advance the counter
do {
old = (int)cri_atomic_read(count);
} while (!cri_cmp_swap(count, old, old + 1));
if (old > 1) {
// Not the outermost, so proceed normally
cri_red_lock(&cri_cs_lock);
} else if (cri_atomic_read(&cri_live_count) || cri_red_trylock(&cri_cs_lock)) {
// PENDING - let it proceed if ready, but retry regardless
#if 1
/* XXX: What the heck is this??
This is a no-op that causes the kernel to re-evaluate the set of
pending signals.
It is a work around for some lost signals I sometimes encounter.
The real problem is most likely somewhere on the kernel side of things. */
sigset_t mask;
sigemptyset(&mask);
sigprocmask(SIG_UNBLOCK, &mask, NULL);
#endif
poll_checkpoint(info); /* decrements counter as a side effect */
return 0;
}
// else lock was acquired by the cri_read_trylock in the conditional.
return 1;
}
// XXX: Unused 'id' argument should be used for debugging.
// XXX: we could also double check that (id == CR_ID_CALLBACK)
// if and only if the state is CR_STATE_ACTIVE.
//
// Returns the current state.
//
// Signal safe because if a signal takes us into the ACTIVE state
// it will also leave the ACTIVE state before we regain control.
//
// NOTE: Now "internal" rather than "private"
int
cri_do_enter(cri_info_t *info,
cr_client_id_t id)
{
int state;
state = cri_atomic_read(&info->cr_state);
if (state != CR_STATE_ACTIVE) {
CRI_WHILE_COND_YIELD(!try_enter(info));
}
return state;
}
// XXX: Unused 'id' argument should be used for debugging.
// XXX: we could also double check that (id == CR_ID_CALLBACK)
// if and only if the state is CR_STATE_ACTIVE.
//
// Returns non-zero on successful entry
//
// Signal safe because if a signal takes us into the ACTIVE state
// it will also leave the ACTIVE state before we regain control.
//
// NOTE: Now "internal" rather than "private"
int
cri_do_tryenter(cri_info_t *info,
cr_client_id_t id)
{
return ((cri_atomic_read(&info->cr_state) == CR_STATE_ACTIVE) || try_enter(info));
}
// XXX: Unused 'id' argument should be used for debugging.
//
// NOTE: Now "internal" rather than "private"
void
cri_do_leave(cri_info_t *info,
cr_client_id_t id)
{
if (cri_atomic_read(&info->cr_state) != CR_STATE_ACTIVE) {
cri_red_unlock(&cri_cs_lock);
poll_checkpoint(info);
}
}
// Not reentrant. Must be called inside a critical section.
static cr_callback_id_t
cri_register_signal(cri_info_t* info,
cr_callback_t func,
void* arg,
int flags)
{
return cri_do_register(info, func, arg, flags);
}
// Not reentrant. Must be called inside a critical section.
static int
cri_replace_signal(cri_info_t *info,
cr_callback_id_t id,
cr_callback_t func,
void* arg,
int flags)
{
return cri_do_replace(info, id, func, arg, flags);
}
//
// "Public" data
//
//
// "Public" functions
//
// Not reentrant. Must be called inside a critical section.
cr_callback_id_t
cri_do_register(cri_info_t *info,
cr_callback_t func,
void* arg,
int flags)
{
int indx = info->cr_cb_count;
if (indx < CR_MAX_CALLBACKS) {
int next = indx + 1;
// Grow on demand
info->cr_cb = realloc(info->cr_cb, next * sizeof(*info->cr_cb));
if (!info->cr_cb) {
// Assume that errno==ENOMEM as required Unix98 standard
return -1;
}
// Set entry before advancing the count
info->cr_cb[indx].func = func;
info->cr_cb[indx].arg = arg;
info->cr_cb[indx].flags = flags;
info->cr_cb_count = next;
return indx;
} else {
errno = ENOSPC;
return -1;
}
}
// Note that we don't replace 'func', 'arg' and 'flags' atomically.
// Note that we ensure the context is not changed.
// Such atomicity is the responsibility of the caller.
//
// Not reentrant. Must be called inside a critical section.
// Not exposed to user.
int
cri_do_replace(cri_info_t *info,
cr_callback_id_t id,
cr_callback_t func,
void* arg,
int flags)
{
int retval = -1;
errno = EINVAL;
if ((flags & CRI_CONTEXT_MASK) == (id & CRI_CONTEXT_MASK)) {
id &= ~CRI_CONTEXT_MASK;
if ((id >= 0) && (id < info->cr_cb_count)) {
info->cr_cb[id].func = func;
info->cr_cb[id].arg = arg;
info->cr_cb[id].flags = flags;
retval = 0;
} else {
/* id out-of-bounds */
}
} else {
/* Context mismatch */
}
return retval;
}
cr_callback_id_t
cr_register_callback(cr_callback_t func,
void* arg,
int flags)
{
cri_info_t *info = CRI_INFO_OR_RETURN(-1); // thread-specific
int context = 0; // silence a "used uninitialized" warning
int retval = -1; // assume failure
int state;
state = cri_do_enter(info, CRI_ID_INTERNAL);
errno = EBUSY;
if (state == CR_STATE_ACTIVE) {
// Called from a callback! retval and errno are already set
goto out;
}
errno = EINVAL;
context = flags & CRI_CONTEXT_MASK;
switch (context) {
case CR_SIGNAL_CONTEXT:
retval = cri_register_signal(info, func, arg, flags);
break;
case CR_THREAD_CONTEXT:
retval = cri_register_thread(info, func, arg, flags);
break;
//default: Bad flags! retval and errno are already set
}
out:
cri_do_leave(info, CRI_ID_INTERNAL);
return (retval >= 0) ? (retval | context) : retval;
}
// Not reentrant.
int
cr_replace_callback(cr_callback_id_t id,
cr_callback_t func,
void* arg,
int flags)
{
cri_info_t *info = CRI_INFO_OR_RETURN(-1); // thread-specific
int retval = -1; // Assume failure
int state;
state = cri_do_enter(info, CRI_ID_INTERNAL);
errno = EBUSY;
if (state == CR_STATE_ACTIVE) {
// Called from a callback! retval and errno are already set
goto out;
}
errno = EINVAL;
switch (flags & CRI_CONTEXT_MASK) {
case CR_SIGNAL_CONTEXT:
retval = cri_replace_signal(info, id, func, arg, flags);
break;
case CR_THREAD_CONTEXT:
retval = cri_replace_thread(info, id, func, arg, flags);
break;
//default: Bad flags! retval and errno are already set
}
out:
cri_do_leave(info, CRI_ID_INTERNAL);
return retval;
}
// Not reentrant.
int
cr_replace_self(cr_callback_t func,
void* arg,
int flags)
{
cri_info_t *info = CRI_CB_INFO_OR_RETURN(-1); // thread-specific
cr_callback_id_t id;
/* form the full id from the index and context */
id = info->run.id;
id |= (info->cr_cb[id].flags & CRI_CONTEXT_MASK);
return cri_do_replace(info, id, func, arg, flags);
}
int
cr_status(void)
{
cri_info_t *info = CRI_INFO_OR_RETURN(-1); // thread-specific
return do_state(info);
}
// XXX: Unused 'id' argument should be used for debugging.
int
cr_enter_cs(cr_client_id_t id)
{
cri_info_t *info = CRI_INFO_OR_RETURN(-1); // thread-specific
cri_do_enter(info, id);
return 0;
}
// XXX: Unused 'id' argument should be used for debugging.
int
cr_tryenter_cs(cr_client_id_t id)
{
cri_info_t *info = CRI_INFO_OR_RETURN(-1); // thread-specific
return !cri_do_tryenter(info, id);
}
// XXX: Unused 'id' argument should be used for debugging.
int
cr_leave_cs(cr_client_id_t id)
{
cri_info_t *info = CRI_INFO_OR_RETURN(-1); // thread-specific
cri_do_leave(info, id);
return 0;
}
// Return address of the per-checkpoint/per-thread info
const struct cr_checkpoint_info * cr_get_checkpoint_info(void)
{
cri_info_t *info = cri_info_location(); // thread-specific
struct cr_checkpoint_info *result;
if (!info || cri_atomic_read(&info->cr_state) != CR_STATE_ACTIVE) {
return NULL;
}
result = &(info->cr_checkpoint_info);
if (result->dest == NULL) {
struct cr_chkpt_info tmp;
int rc;
tmp.dest = info->path;
rc = cri_syscall_token(info->run.token, CR_OP_HAND_CHKPT_INFO, (uintptr_t)&tmp);
if (rc != 0) {
CRI_ABORT("CR_OP_HAND_CHKPT_INFO returned w/ errno=%d",
errno);
}
result->requester = tmp.requester;
result->target = tmp.target;
result->scope = tmp.scope;
result->signal = tmp.signal;
result->dest = tmp.dest;
LIBCR_TRACE(LIBCR_TRACE_INFO, "requester=%d target=%d scope=%d signal=%d dest='%s'",
tmp.requester, tmp.target, tmp.scope, tmp.signal, tmp.dest);
}
return result;
}
// Return address of the per-restart/per-thread info
const struct cr_restart_info * cr_get_restart_info(void)
{
cri_info_t *info = cri_info_location(); // thread-specific
struct cr_restart_info *result;
if (!info || cri_atomic_read(&info->cr_state) != CR_STATE_ACTIVE) {
return NULL;
}
result = &(info->cr_restart_info);
result->requester = info->run.rc; // Pid of cr_restart was returned from syscall
if (result->src == NULL) {
int rc = cri_syscall_token(info->run.token, CR_OP_HAND_SRC, (uintptr_t)info->path);
if (rc != 0) {
CRI_ABORT("CR_OP_HAND_SRC returned w/ errno=%d",
errno);
}
result->src = info->path;
}
return result;
}
// Return a client identifier used to invoke cr_{enter,leave}_cs().
// Also registers the handler on first call per thread.
// May later setup additional state.
cr_client_id_t cr_init(void)
{
cri_info_t *info;
int token;
int rc;
// First establish connection to verify that we have kernel support
token = cri_connect();
if (token < 0) {
return token;
}
info = cri_info_init(); // thread-specific
if (!info->handler) {
// Set the handler
info->handler = &my_handler;
// Register ourself with the kernel
do {
rc = cri_syscall_token(token, CR_OP_HAND_PHASE2, token);
} while ((rc < 0) && (errno == EAGAIN));
if (rc != 0) {
CRI_ABORT("CR_OP_HAND_PHASE2 returned w/ errno = %d", errno);
}
}
return info->next_id++;
}
// Read and potentialy write info->hold
// This controls whether the post-handler barrier is blocking or not.
int cr_hold_ctrl(int scope, int flags)
{
cri_info_t *info = CRI_INFO_OR_RETURN(-1); // thread-specific
cri_atomic_t *p;
int oldval;
switch (scope) {
case CR_HOLD_SCOPE_THREAD:
p = &info->hold;
break;
case CR_HOLD_SCOPE_INIT:
p = &cri_hold_init;
break;
case CR_HOLD_SCOPE_UNINIT:
p = &cri_hold_uninit;
break;
default:
errno = EINVAL;
return -1;
}
oldval = cri_atomic_read(p);
if (flags == CR_HOLD_READ) {
// Nothing more to do
} else if (!(flags & ~CR_HOLD_BOTH) ||
((scope == CR_HOLD_SCOPE_THREAD) && (flags == CR_HOLD_DFLT))) {
/* ensure meaningful oldval in presence of threads and signals: */
while (!cri_cmp_swap(p, oldval, flags)) { oldval = cri_atomic_read(p); }
} else {
errno = EINVAL;
oldval = -1;
}
return oldval;
}
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