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Merge "sched: Don't allow ast_sched_del to deadlock ast_sched_runq from same thread" into 13

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This commit is contained in:
George Joseph
2019-07-19 08:46:29 -05:00
committed by Gerrit Code Review
parent 284b657539 3449240130
commit 8d1acc27d5
2 changed files with 32 additions and 14 deletions
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16
include/asterisk/sched.h
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@@ -71,20 +71,24 @@ extern "C" {
/*! /*!
* \brief schedule task to get deleted and call unref function * \brief schedule task to get deleted and call unref function
*
* Only calls unref function if the delete succeeded.
*
* \sa AST_SCHED_DEL * \sa AST_SCHED_DEL
* \since 1.6.1 * \since 1.6.1
*/ */
#define AST_SCHED_DEL_UNREF(sched, id, refcall) \ #define AST_SCHED_DEL_UNREF(sched, id, refcall) \
do { \ do { \
int _count = 0; \ int _count = 0, _id; \
while (id > -1 && ast_sched_del(sched, id) && ++_count < 10) { \ while ((_id = id) > -1 && ast_sched_del(sched, _id) && ++_count < 10) { \
usleep(1); \ usleep(1); \
} \ } \
if (_count == 10) \ if (_count == 10) { \
ast_log(LOG_WARNING, "Unable to cancel schedule ID %d. This is probably a bug (%s: %s, line %d).\n", id, __FILE__, __PRETTY_FUNCTION__, __LINE__); \ ast_log(LOG_WARNING, "Unable to cancel schedule ID %d. This is probably a bug (%s: %s, line %d).\n", _id, __FILE__, __PRETTY_FUNCTION__, __LINE__); \
if (id > -1) \ } else if (_id > -1) { \
refcall; \ refcall; \
id = -1; \ id = -1; \
} \
} while (0); } while (0);
/*! /*!

30
main/sched.c
View File

@@ -118,6 +118,8 @@ struct ast_sched_context {
struct sched_thread *sched_thread; struct sched_thread *sched_thread;
/*! The scheduled task that is currently executing */ /*! The scheduled task that is currently executing */
struct sched *currently_executing; struct sched *currently_executing;
/*! Valid while currently_executing is not NULL */
pthread_t executing_thread_id;
#ifdef SCHED_MAX_CACHE #ifdef SCHED_MAX_CACHE
AST_LIST_HEAD_NOLOCK(, sched) schedc; /*!< Cache of unused schedule structures and how many */ AST_LIST_HEAD_NOLOCK(, sched) schedc; /*!< Cache of unused schedule structures and how many */
@@ -627,15 +629,26 @@ int ast_sched_del(struct ast_sched_context *con, int id)
} }
sched_release(con, s); sched_release(con, s);
} else if (con->currently_executing && (id == con->currently_executing->sched_id->id)) { } else if (con->currently_executing && (id == con->currently_executing->sched_id->id)) {
s = con->currently_executing; if (con->executing_thread_id == pthread_self()) {
s->deleted = 1; /* The scheduled callback is trying to delete itself.
/* Wait for executing task to complete so that caller of ast_sched_del() does not * Not good as that is a deadlock. */
* free memory out from under the task. ast_log(LOG_ERROR,
*/ "BUG! Trying to delete sched %d from within the callback %p. "
while (con->currently_executing && (id == con->currently_executing->sched_id->id)) { "Ignoring so we don't deadlock\n",
ast_cond_wait(&s->cond, &con->lock); id, con->currently_executing->callback);
ast_log_backtrace();
/* We'll return -1 below because s is NULL.
* The caller will rightly assume that the unscheduling failed. */
} else {
s = con->currently_executing;
s->deleted = 1;
/* Wait for executing task to complete so that the caller of
* ast_sched_del() does not free memory out from under the task. */
while (con->currently_executing && (id == con->currently_executing->sched_id->id)) {
ast_cond_wait(&s->cond, &con->lock);
}
/* Do not sched_release() here because ast_sched_runq() will do it */
} }
/* Do not sched_release() here because ast_sched_runq() will do it */
} }
#ifdef DUMP_SCHEDULER #ifdef DUMP_SCHEDULER
@@ -775,6 +788,7 @@ int ast_sched_runq(struct ast_sched_context *con)
*/ */
con->currently_executing = current; con->currently_executing = current;
con->executing_thread_id = pthread_self();
ast_mutex_unlock(&con->lock); ast_mutex_unlock(&con->lock);
res = current->callback(current->data); res = current->callback(current->data);
ast_mutex_lock(&con->lock); ast_mutex_lock(&con->lock);