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/*-
* Copyright (c) 2014-2016 MongoDB, Inc.
* Copyright (c) 2008-2014 WiredTiger, Inc.
* All rights reserved.
*
* See the file LICENSE for redistribution information.
*/
#include "wt_internal.h"
/*
* __thread_run --
* General wrapper for any thread.
*/
static WT_THREAD_RET
__thread_run(void *arg)
{
WT_DECL_RET;
WT_SESSION_IMPL *session;
WT_THREAD *thread;
thread = (WT_THREAD*)arg;
session = thread->session;
for (;;) {
if (!F_ISSET(thread, WT_THREAD_RUN))
break;
if (!F_ISSET(thread, WT_THREAD_ACTIVE))
__wt_cond_wait(session, thread->pause_cond,
WT_THREAD_PAUSE * WT_MILLION, thread->chk_func);
WT_ERR(thread->run_func(session, thread));
}
/*
* If a thread is stopping it may have subsystem cleanup to do.
*/
err: if (thread->stop_func != NULL)
ret = thread->stop_func(session, thread);
if (ret != 0 && F_ISSET(thread, WT_THREAD_PANIC_FAIL))
WT_PANIC_MSG(session, ret,
"Unrecoverable utility thread error");
/*
* The three cases when threads are expected to stop are:
* 1. When recovery is done.
* 2. When the connection is closing.
* 3. When a shutdown has been requested via clearing the run flag.
*/
WT_ASSERT(session, !F_ISSET(thread, WT_THREAD_RUN) ||
F_ISSET(S2C(session), WT_CONN_CLOSING | WT_CONN_RECOVERING));
return (WT_THREAD_RET_VALUE);
}
/*
* __thread_group_shrink --
* Decrease the number of threads in the group and free memory
* associated with slots larger than the new count.
*/
static int
__thread_group_shrink(
WT_SESSION_IMPL *session, WT_THREAD_GROUP *group, uint32_t new_count)
{
WT_DECL_RET;
WT_SESSION *wt_session;
WT_THREAD *thread;
uint32_t current_slot;
WT_ASSERT(session, __wt_rwlock_islocked(session, &group->lock));
for (current_slot = group->alloc; current_slot > new_count; ) {
/*
* The offset value is a counter not an array index,
* so adjust it before finding the last thread in the group.
*/
thread = group->threads[--current_slot];
if (thread == NULL)
continue;
/* Wake threads to ensure they notice the state change */
WT_ASSERT(session, thread->tid != 0);
__wt_verbose(session, WT_VERB_THREAD_GROUP,
"Stopping utility thread: %p:%" PRIu32,
(void *)group, thread->id);
if (F_ISSET(thread, WT_THREAD_ACTIVE))
--group->current_threads;
F_CLR(thread, WT_THREAD_ACTIVE | WT_THREAD_RUN);
/*
* Signal the thread in case it is in a long timeout.
*/
__wt_cond_signal(session, thread->pause_cond);
__wt_cond_signal(session, group->wait_cond);
WT_TRET(__wt_thread_join(session, thread->tid));
WT_TRET(__wt_cond_destroy(session, &thread->pause_cond));
WT_ASSERT(session, thread->session != NULL);
wt_session = (WT_SESSION *)thread->session;
WT_TRET(wt_session->close(wt_session, NULL));
thread->session = NULL;
__wt_free(session, thread);
group->threads[current_slot] = NULL;
}
return (ret);
}
/*
* __thread_group_resize --
* Resize an array of utility threads already holding the lock.
*/
static int
__thread_group_resize(
WT_SESSION_IMPL *session, WT_THREAD_GROUP *group,
uint32_t new_min, uint32_t new_max, uint32_t flags)
{
WT_CONNECTION_IMPL *conn;
WT_DECL_RET;
WT_THREAD *thread;
size_t alloc;
uint32_t i, session_flags;
conn = S2C(session);
session_flags = 0;
__wt_verbose(session, WT_VERB_THREAD_GROUP,
"Resize thread group: %p, from min: %" PRIu32 " -> %" PRIu32
" from max: %" PRIu32 " -> %" PRIu32,
(void *)group, group->min, new_min, group->max, new_max);
WT_ASSERT(session,
group->current_threads <= group->alloc &&
__wt_rwlock_islocked(session, &group->lock));
if (new_min == group->min && new_max == group->max)
return (0);
if (new_min > new_max)
return (EINVAL);
/*
* Call shrink to reduce the number of thread structures and running
* threads if required by the change in group size.
*/
WT_RET(__thread_group_shrink(session, group, new_max));
/*
* Only reallocate the thread array if it is the largest ever, since
* our realloc doesn't support shrinking the allocated size.
*/
if (group->alloc < new_max) {
alloc = group->alloc * sizeof(*group->threads);
WT_RET(__wt_realloc(session, &alloc,
new_max * sizeof(*group->threads), &group->threads));
group->alloc = new_max;
}
/*
* Initialize the structures based on the previous group size, not
* the previous allocated size.
*/
for (i = group->max; i < new_max; i++) {
WT_ERR(__wt_calloc_one(session, &thread));
/*
* Threads get their own session and lookaside table cursor
* if the lookaside table is open. Note that threads are
* started during recovery, before the lookaside table is
* created.
*/
if (LF_ISSET(WT_THREAD_CAN_WAIT))
session_flags = WT_SESSION_CAN_WAIT;
if (F_ISSET(conn, WT_CONN_LAS_OPEN))
FLD_SET(session_flags, WT_SESSION_LOOKASIDE_CURSOR);
WT_ERR(__wt_open_internal_session(conn, group->name,
false, session_flags, &thread->session));
if (LF_ISSET(WT_THREAD_PANIC_FAIL))
F_SET(thread, WT_THREAD_PANIC_FAIL);
thread->id = i;
thread->chk_func = group->chk_func;
thread->run_func = group->run_func;
thread->stop_func = group->stop_func;
WT_ERR(__wt_cond_alloc(
session, "Thread cond", &thread->pause_cond));
WT_ASSERT(session, group->threads[i] == NULL);
group->threads[i] = thread;
/*
* Start thread as inactive. We'll activate the needed
* number later.
*/
__wt_verbose(session, WT_VERB_THREAD_GROUP,
"Starting utility thread: %p:%" PRIu32,
(void *)group, thread->id);
F_SET(thread, WT_THREAD_RUN);
WT_ASSERT(session, thread->session != NULL);
WT_ERR(__wt_thread_create(thread->session,
&thread->tid, __thread_run, thread));
}
err: /*
* Update the thread group information even on failure to improve our
* chances of cleaning up properly.
*/
group->max = new_max;
group->min = new_min;
/*
* An error resizing a thread array is fatal, it should only happen
* in an out of memory situation.
*/
if (ret == 0)
while (group->current_threads < new_min)
__wt_thread_group_start_one(session, group, true);
else {
WT_TRET(__wt_thread_group_destroy(session, group));
WT_PANIC_RET(session, ret, "Error while resizing thread group");
}
return (ret);
}
/*
* __wt_thread_group_resize --
* Resize an array of utility threads taking the lock.
*/
int
__wt_thread_group_resize(
WT_SESSION_IMPL *session, WT_THREAD_GROUP *group,
uint32_t new_min, uint32_t new_max, uint32_t flags)
{
WT_DECL_RET;
__wt_writelock(session, &group->lock);
WT_TRET(__thread_group_resize(session, group, new_min, new_max, flags));
__wt_writeunlock(session, &group->lock);
return (ret);
}
/*
* __wt_thread_group_create --
* Create a new thread group, assumes incoming group structure is
* zero initialized.
*/
int
__wt_thread_group_create(
WT_SESSION_IMPL *session, WT_THREAD_GROUP *group, const char *name,
uint32_t min, uint32_t max, uint32_t flags,
bool (*chk_func)(WT_SESSION_IMPL *session),
int (*run_func)(WT_SESSION_IMPL *session, WT_THREAD *context),
int (*stop_func)(WT_SESSION_IMPL *session, WT_THREAD *context))
{
WT_DECL_RET;
bool cond_alloced;
/* Check that the structure is initialized as expected */
WT_ASSERT(session, group->alloc == 0);
cond_alloced = false;
__wt_verbose(session, WT_VERB_THREAD_GROUP,
"Creating thread group: %p", (void *)group);
__wt_rwlock_init(session, &group->lock);
WT_ERR(__wt_cond_alloc(
session, "thread group cond", &group->wait_cond));
cond_alloced = true;
__wt_writelock(session, &group->lock);
group->chk_func = chk_func;
group->run_func = run_func;
group->stop_func = stop_func;
group->name = name;
WT_TRET(__thread_group_resize(session, group, min, max, flags));
__wt_writeunlock(session, &group->lock);
/* Cleanup on error to avoid leaking resources */
err: if (ret != 0) {
if (cond_alloced)
WT_TRET(__wt_cond_destroy(session, &group->wait_cond));
__wt_rwlock_destroy(session, &group->lock);
}
return (ret);
}
/*
* __wt_thread_group_destroy --
* Shut down a thread group. Our caller must hold the lock.
*/
int
__wt_thread_group_destroy(WT_SESSION_IMPL *session, WT_THREAD_GROUP *group)
{
WT_DECL_RET;
__wt_verbose(session, WT_VERB_THREAD_GROUP,
"Destroying thread group: %p", (void *)group);
WT_ASSERT(session, __wt_rwlock_islocked(session, &group->lock));
/* Shut down all threads and free associated resources. */
WT_TRET(__thread_group_shrink(session, group, 0));
__wt_free(session, group->threads);
WT_TRET(__wt_cond_destroy(session, &group->wait_cond));
__wt_rwlock_destroy(session, &group->lock);
/*
* Clear out any settings from the group, some structures are reused
* for different thread groups - in particular the eviction thread
* group for recovery and then normal runtime.
*/
memset(group, 0, sizeof(*group));
return (ret);
}
/*
* __wt_thread_group_start_one --
* Start a new thread if possible.
*/
void
__wt_thread_group_start_one(
WT_SESSION_IMPL *session, WT_THREAD_GROUP *group, bool is_locked)
{
WT_THREAD *thread;
if (group->current_threads >= group->max)
return;
if (!is_locked)
__wt_writelock(session, &group->lock);
/* Recheck the bounds now that we hold the lock */
if (group->current_threads < group->max) {
thread = group->threads[group->current_threads++];
WT_ASSERT(session, thread != NULL);
__wt_verbose(session, WT_VERB_THREAD_GROUP,
"Activating utility thread: %p:%" PRIu32,
(void *)group, thread->id);
WT_ASSERT(session, !F_ISSET(thread, WT_THREAD_ACTIVE));
F_SET(thread, WT_THREAD_ACTIVE);
__wt_cond_signal(session, thread->pause_cond);
}
if (!is_locked)
__wt_writeunlock(session, &group->lock);
}
/*
* __wt_thread_group_stop_one --
* Pause one thread if possible.
*/
void
__wt_thread_group_stop_one(WT_SESSION_IMPL *session, WT_THREAD_GROUP *group)
{
WT_THREAD *thread;
if (group->current_threads <= group->min)
return;
__wt_writelock(session, &group->lock);
/* Recheck the bounds now that we hold the lock */
if (group->current_threads > group->min) {
thread = group->threads[--group->current_threads];
__wt_verbose(session, WT_VERB_THREAD_GROUP,
"Pausing utility thread: %p:%" PRIu32,
(void *)group, thread->id);
WT_ASSERT(session, F_ISSET(thread, WT_THREAD_ACTIVE));
F_CLR(thread, WT_THREAD_ACTIVE);
__wt_cond_signal(session, thread->pause_cond);
}
__wt_writeunlock(session, &group->lock);
}
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