pthreadpool: implement pthreadpool_tevent_wrapper_create() infrastructure
authorStefan Metzmacher <metze@samba.org>
Fri, 20 Apr 2018 15:12:07 +0000 (17:12 +0200)
committerRalph Boehme <slow@samba.org>
Tue, 24 Jul 2018 15:38:28 +0000 (17:38 +0200)
This can be used implement a generic per thread impersonation
for thread pools.

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>
lib/pthreadpool/pthreadpool_tevent.c
lib/pthreadpool/pthreadpool_tevent.h

index 01e8586..19b1e6d 100644 (file)
@@ -103,6 +103,8 @@ struct pthreadpool_tevent_glue {
        /* Tuple we are keeping track of in this list. */
        struct tevent_context *ev;
        struct tevent_threaded_context *tctx;
+       /* recheck monitor fd event */
+       struct tevent_fd *fde;
        /* Pointer to link object owned by *ev. */
        struct pthreadpool_tevent_glue_ev_link *ev_link;
        /* active jobs */
@@ -122,11 +124,33 @@ struct pthreadpool_tevent_glue_ev_link {
        struct pthreadpool_tevent_glue *glue;
 };
 
+struct pthreadpool_tevent_wrapper {
+       struct pthreadpool_tevent *main_tp;
+       struct pthreadpool_tevent *wrap_tp;
+       const struct pthreadpool_tevent_wrapper_ops *ops;
+       void *private_state;
+       bool force_per_thread_cwd;
+};
+
 struct pthreadpool_tevent {
+       struct pthreadpool_tevent *prev, *next;
+
        struct pthreadpool *pool;
        struct pthreadpool_tevent_glue *glue_list;
 
        struct pthreadpool_tevent_job *jobs;
+
+       struct {
+               /*
+                * This is used on the main context
+                */
+               struct pthreadpool_tevent *list;
+
+               /*
+                * This is used on the wrapper context
+                */
+               struct pthreadpool_tevent_wrapper *ctx;
+       } wrapper;
 };
 
 struct pthreadpool_tevent_job_state {
@@ -141,6 +165,7 @@ struct pthreadpool_tevent_job {
        struct pthreadpool_tevent_job *prev, *next;
 
        struct pthreadpool_tevent *pool;
+       struct pthreadpool_tevent_wrapper *wrapper;
        struct pthreadpool_tevent_job_state *state;
        struct tevent_immediate *im;
 
@@ -180,6 +205,15 @@ struct pthreadpool_tevent_job {
                 */
                bool started;
 
+               /*
+                * 'wrapper'
+                * set before calling the wrapper before_job() or
+                * after_job() hooks.
+                * unset again check the hook finished.
+                * (only written by job thread!)
+                */
+               bool wrapper;
+
                /*
                 * 'executed'
                 * set once the job function returned.
@@ -209,6 +243,18 @@ struct pthreadpool_tevent_job {
                 * (only written by job thread!)
                 */
                bool signaled;
+
+               /*
+                * 'exit_thread'
+                * maybe set during pthreadpool_tevent_job_fn()
+                * if some wrapper related code generated an error
+                * and the environment isn't safe anymore.
+                *
+                * In such a case pthreadpool_tevent_job_signal()
+                * will pick this up and therminate the current
+                * worker thread by returning -1.
+                */
+               bool exit_thread; /* only written/read by job thread! */
        } needs_fence;
 
        bool per_thread_cwd;
@@ -267,8 +313,22 @@ int pthreadpool_tevent_init(TALLOC_CTX *mem_ctx, unsigned max_threads,
        return 0;
 }
 
+static struct pthreadpool_tevent *pthreadpool_tevent_unwrap(
+       struct pthreadpool_tevent *pool)
+{
+       struct pthreadpool_tevent_wrapper *wrapper = pool->wrapper.ctx;
+
+       if (wrapper != NULL) {
+               return wrapper->main_tp;
+       }
+
+       return pool;
+}
+
 size_t pthreadpool_tevent_max_threads(struct pthreadpool_tevent *pool)
 {
+       pool = pthreadpool_tevent_unwrap(pool);
+
        if (pool->pool == NULL) {
                return 0;
        }
@@ -278,6 +338,8 @@ size_t pthreadpool_tevent_max_threads(struct pthreadpool_tevent *pool)
 
 size_t pthreadpool_tevent_queued_jobs(struct pthreadpool_tevent *pool)
 {
+       pool = pthreadpool_tevent_unwrap(pool);
+
        if (pool->pool == NULL) {
                return 0;
        }
@@ -287,6 +349,14 @@ size_t pthreadpool_tevent_queued_jobs(struct pthreadpool_tevent *pool)
 
 bool pthreadpool_tevent_per_thread_cwd(struct pthreadpool_tevent *pool)
 {
+       struct pthreadpool_tevent_wrapper *wrapper = pool->wrapper.ctx;
+
+       if (wrapper != NULL && wrapper->force_per_thread_cwd) {
+               return true;
+       }
+
+       pool = pthreadpool_tevent_unwrap(pool);
+
        if (pool->pool == NULL) {
                return false;
        }
@@ -298,21 +368,94 @@ static int pthreadpool_tevent_destructor(struct pthreadpool_tevent *pool)
 {
        struct pthreadpool_tevent_job *job = NULL;
        struct pthreadpool_tevent_job *njob = NULL;
+       struct pthreadpool_tevent *wrap_tp = NULL;
+       struct pthreadpool_tevent *nwrap_tp = NULL;
        struct pthreadpool_tevent_glue *glue = NULL;
        int ret;
 
+       if (pool->wrapper.ctx != NULL) {
+               struct pthreadpool_tevent_wrapper *wrapper = pool->wrapper.ctx;
+
+               pool->wrapper.ctx = NULL;
+               pool = wrapper->main_tp;
+
+               DLIST_REMOVE(pool->wrapper.list, wrapper->wrap_tp);
+
+               for (job = pool->jobs; job != NULL; job = njob) {
+                       njob = job->next;
+
+                       if (job->wrapper != wrapper) {
+                               continue;
+                       }
+
+                       /*
+                        * This removes the job from the list
+                        *
+                        * Note that it waits in case
+                        * the wrapper hooks are currently
+                        * executing on the job.
+                        */
+                       pthreadpool_tevent_job_orphan(job);
+               }
+
+               /*
+                * At this point we're sure that no job
+                * still references the pthreadpool_tevent_wrapper
+                * structure, so we can free it.
+                */
+               TALLOC_FREE(wrapper);
+
+               pthreadpool_tevent_cleanup_orphaned_jobs();
+               return 0;
+       }
+
+       if (pool->pool == NULL) {
+               /*
+                * A dangling wrapper without main_tp.
+                */
+               return 0;
+       }
+
        ret = pthreadpool_stop(pool->pool);
        if (ret != 0) {
                return ret;
        }
 
+       /*
+        * orphan all jobs (including wrapper jobs)
+        */
        for (job = pool->jobs; job != NULL; job = njob) {
                njob = job->next;
 
-               /* The job this removes it from the list */
+               /*
+                * The job this removes it from the list
+                *
+                * Note that it waits in case
+                * the wrapper hooks are currently
+                * executing on the job (thread).
+                */
                pthreadpool_tevent_job_orphan(job);
        }
 
+       /*
+        * cleanup all existing wrappers, remember we just orphaned
+        * all jobs (including the once of the wrappers).
+        *
+        * So we just mark as broken, so that
+        * pthreadpool_tevent_job_send() won't accept new jobs.
+        */
+       for (wrap_tp = pool->wrapper.list; wrap_tp != NULL; wrap_tp = nwrap_tp) {
+               nwrap_tp = wrap_tp->next;
+
+               /*
+                * Just mark them as broken, so that we can't
+                * get more jobs.
+                */
+               TALLOC_FREE(wrap_tp->wrapper.ctx);
+
+               DLIST_REMOVE(pool->wrapper.list, wrap_tp);
+       }
+
        /*
         * Delete all the registered
         * tevent_context/tevent_threaded_context
@@ -335,12 +478,93 @@ static int pthreadpool_tevent_destructor(struct pthreadpool_tevent *pool)
        return 0;
 }
 
+struct pthreadpool_tevent *_pthreadpool_tevent_wrapper_create(
+                               struct pthreadpool_tevent *main_tp,
+                               TALLOC_CTX *mem_ctx,
+                               const struct pthreadpool_tevent_wrapper_ops *ops,
+                               void *pstate,
+                               size_t psize,
+                               const char *type,
+                               const char *location)
+{
+       void **ppstate = (void **)pstate;
+       struct pthreadpool_tevent *wrap_tp = NULL;
+       struct pthreadpool_tevent_wrapper *wrapper = NULL;
+
+       pthreadpool_tevent_cleanup_orphaned_jobs();
+
+       if (main_tp->wrapper.ctx != NULL) {
+               /*
+                * stacking of wrappers is not supported
+                */
+               errno = EINVAL;
+               return NULL;
+       }
+
+       if (main_tp->pool == NULL) {
+               /*
+                * The pool is no longer valid,
+                * most likely it was a wrapper context
+                * where the main pool was destroyed.
+                */
+               errno = EINVAL;
+               return NULL;
+       }
+
+       wrap_tp = talloc_zero(mem_ctx, struct pthreadpool_tevent);
+       if (wrap_tp == NULL) {
+               return NULL;
+       }
+
+       wrapper = talloc_zero(wrap_tp, struct pthreadpool_tevent_wrapper);
+       if (wrapper == NULL) {
+               TALLOC_FREE(wrap_tp);
+               return NULL;
+       }
+       wrapper->main_tp = main_tp;
+       wrapper->wrap_tp = wrap_tp;
+       wrapper->ops = ops;
+       wrapper->private_state = talloc_zero_size(wrapper, psize);
+       if (wrapper->private_state == NULL) {
+               TALLOC_FREE(wrap_tp);
+               return NULL;
+       }
+       talloc_set_name_const(wrapper->private_state, type);
+
+       wrap_tp->wrapper.ctx = wrapper;
+
+       DLIST_ADD_END(main_tp->wrapper.list, wrap_tp);
+
+       talloc_set_destructor(wrap_tp, pthreadpool_tevent_destructor);
+
+       *ppstate = wrapper->private_state;
+       return wrap_tp;
+}
+
+void pthreadpool_tevent_force_per_thread_cwd(struct pthreadpool_tevent *pool,
+                                            const void *private_state)
+{
+       struct pthreadpool_tevent_wrapper *wrapper = pool->wrapper.ctx;
+
+       if (wrapper == NULL) {
+               abort();
+       }
+
+       if (wrapper->private_state != private_state) {
+               abort();
+       }
+
+       wrapper->force_per_thread_cwd = true;
+}
+
 static int pthreadpool_tevent_glue_destructor(
        struct pthreadpool_tevent_glue *glue)
 {
        struct pthreadpool_tevent_job_state *state = NULL;
        struct pthreadpool_tevent_job_state *nstate = NULL;
 
+       TALLOC_FREE(glue->fde);
+
        for (state = glue->states; state != NULL; state = nstate) {
                nstate = state->next;
 
@@ -381,6 +605,59 @@ static int pthreadpool_tevent_glue_link_destructor(
        return 0;
 }
 
+static void pthreadpool_tevent_glue_monitor(struct tevent_context *ev,
+                                           struct tevent_fd *fde,
+                                           uint16_t flags,
+                                           void *private_data)
+{
+       struct pthreadpool_tevent_glue *glue =
+               talloc_get_type_abort(private_data,
+               struct pthreadpool_tevent_glue);
+       struct pthreadpool_tevent_job *job = NULL;
+       struct pthreadpool_tevent_job *njob = NULL;
+       int ret = -1;
+
+       ret = pthreadpool_restart_check_monitor_drain(glue->pool->pool);
+       if (ret != 0) {
+               TALLOC_FREE(glue->fde);
+       }
+
+       ret = pthreadpool_restart_check(glue->pool->pool);
+       if (ret == 0) {
+               /*
+                * success...
+                */
+               goto done;
+       }
+
+       /*
+        * There's a problem and the pool
+        * has not a single thread available
+        * for pending jobs, so we can only
+        * stop the jobs and return an error.
+        * This is similar to a failure from
+        * pthreadpool_add_job().
+        */
+       for (job = glue->pool->jobs; job != NULL; job = njob) {
+               njob = job->next;
+
+               tevent_req_defer_callback(job->state->req,
+                                         job->state->ev);
+               tevent_req_error(job->state->req, ret);
+       }
+
+done:
+       if (glue->states == NULL) {
+               /*
+                * If the glue doesn't have any pending jobs
+                * we remove the glue.
+                *
+                * In order to remove the fd event.
+                */
+               TALLOC_FREE(glue);
+       }
+}
+
 static int pthreadpool_tevent_register_ev(
                                struct pthreadpool_tevent *pool,
                                struct pthreadpool_tevent_job_state *state)
@@ -388,6 +665,7 @@ static int pthreadpool_tevent_register_ev(
        struct tevent_context *ev = state->ev;
        struct pthreadpool_tevent_glue *glue = NULL;
        struct pthreadpool_tevent_glue_ev_link *ev_link = NULL;
+       int monitor_fd = -1;
 
        /*
         * See if this tevent_context was already registered by
@@ -420,6 +698,28 @@ static int pthreadpool_tevent_register_ev(
        };
        talloc_set_destructor(glue, pthreadpool_tevent_glue_destructor);
 
+       monitor_fd = pthreadpool_restart_check_monitor_fd(pool->pool);
+       if (monitor_fd == -1 && errno != ENOSYS) {
+               int saved_errno = errno;
+               TALLOC_FREE(glue);
+               return saved_errno;
+       }
+
+       if (monitor_fd != -1) {
+               glue->fde = tevent_add_fd(ev,
+                                         glue,
+                                         monitor_fd,
+                                         TEVENT_FD_READ,
+                                         pthreadpool_tevent_glue_monitor,
+                                         glue);
+               if (glue->fde == NULL) {
+                       close(monitor_fd);
+                       TALLOC_FREE(glue);
+                       return ENOMEM;
+               }
+               tevent_fd_set_auto_close(glue->fde);
+       }
+
        /*
         * Now allocate the link object to the event context. Note this
         * is allocated OFF THE EVENT CONTEXT ITSELF, so if the event
@@ -559,6 +859,24 @@ static void pthreadpool_tevent_job_orphan(struct pthreadpool_tevent_job *job)
                abort();
        }
 
+       /*
+        * Once we marked the request as 'orphaned'
+        * we spin/loop if 'wrapper' is marked as active.
+        *
+        * We need to wait until the wrapper hook finished
+        * before we can set job->wrapper = NULL.
+        *
+        * This is some kind of spinlock, but with
+        * 1 millisecond sleeps in between, in order
+        * to give the thread more cpu time to finish.
+        */
+       PTHREAD_TEVENT_JOB_THREAD_FENCE(job);
+       while (job->needs_fence.wrapper) {
+               poll(NULL, 0, 1);
+               PTHREAD_TEVENT_JOB_THREAD_FENCE(job);
+       }
+       job->wrapper = NULL;
+
        /*
         * Once we marked the request as 'orphaned'
         * we spin/loop if it's already marked
@@ -673,9 +991,14 @@ struct tevent_req *pthreadpool_tevent_job_send(
        struct pthreadpool_tevent_job_state *state = NULL;
        struct pthreadpool_tevent_job *job = NULL;
        int ret;
+       struct pthreadpool_tevent_wrapper *wrapper = pool->wrapper.ctx;
 
        pthreadpool_tevent_cleanup_orphaned_jobs();
 
+       if (wrapper != NULL) {
+               pool = wrapper->main_tp;
+       }
+
        req = tevent_req_create(mem_ctx, &state,
                                struct pthreadpool_tevent_job_state);
        if (req == NULL) {
@@ -705,6 +1028,7 @@ struct tevent_req *pthreadpool_tevent_job_send(
                return tevent_req_post(req, ev);
        }
        job->pool = pool;
+       job->wrapper = wrapper;
        job->fn = fn;
        job->private_data = private_data;
        job->im = tevent_create_immediate(state->job);
@@ -803,15 +1127,73 @@ static void pthreadpool_tevent_job_fn(void *private_data)
        struct pthreadpool_tevent_job *job =
                talloc_get_type_abort(private_data,
                struct pthreadpool_tevent_job);
+       struct pthreadpool_tevent_wrapper *wrapper = NULL;
 
        current_job = job;
        job->needs_fence.started = true;
        PTHREAD_TEVENT_JOB_THREAD_FENCE(job);
+       if (job->needs_fence.orphaned) {
+               current_job = NULL;
+               return;
+       }
+
+       wrapper = job->wrapper;
+       if (wrapper != NULL) {
+               bool ok;
+
+               job->needs_fence.wrapper = true;
+               PTHREAD_TEVENT_JOB_THREAD_FENCE(job);
+               if (job->needs_fence.orphaned) {
+                       job->needs_fence.wrapper = false;
+                       PTHREAD_TEVENT_JOB_THREAD_FENCE(job);
+                       current_job = NULL;
+                       return;
+               }
+               ok = wrapper->ops->before_job(wrapper->wrap_tp,
+                                             wrapper->private_state,
+                                             wrapper->main_tp,
+                                             __location__);
+               job->needs_fence.wrapper = false;
+               PTHREAD_TEVENT_JOB_THREAD_FENCE(job);
+               if (!ok) {
+                       job->needs_fence.exit_thread = true;
+                       PTHREAD_TEVENT_JOB_THREAD_FENCE(job);
+                       current_job = NULL;
+                       return;
+               }
+       }
 
        job->fn(job->private_data);
 
        job->needs_fence.executed = true;
        PTHREAD_TEVENT_JOB_THREAD_FENCE(job);
+
+       if (wrapper != NULL) {
+               bool ok;
+
+               job->needs_fence.wrapper = true;
+               PTHREAD_TEVENT_JOB_THREAD_FENCE(job);
+               if (job->needs_fence.orphaned) {
+                       job->needs_fence.wrapper = false;
+                       job->needs_fence.exit_thread = true;
+                       PTHREAD_TEVENT_JOB_THREAD_FENCE(job);
+                       current_job = NULL;
+                       return;
+               }
+               ok = wrapper->ops->after_job(wrapper->wrap_tp,
+                                            wrapper->private_state,
+                                            wrapper->main_tp,
+                                            __location__);
+               job->needs_fence.wrapper = false;
+               PTHREAD_TEVENT_JOB_THREAD_FENCE(job);
+               if (!ok) {
+                       job->needs_fence.exit_thread = true;
+                       PTHREAD_TEVENT_JOB_THREAD_FENCE(job);
+                       current_job = NULL;
+                       return;
+               }
+       }
+
        current_job = NULL;
 }
 
@@ -830,6 +1212,15 @@ static int pthreadpool_tevent_job_signal(int jobid,
                /* Request already gone */
                job->needs_fence.dropped = true;
                PTHREAD_TEVENT_JOB_THREAD_FENCE(job);
+               if (job->needs_fence.exit_thread) {
+                       /*
+                        * A problem with the wrapper the current job/worker
+                        * thread needs to terminate.
+                        *
+                        * The pthreadpool_tevent is already gone.
+                        */
+                       return -1;
+               }
                return 0;
        }
 
@@ -855,6 +1246,15 @@ static int pthreadpool_tevent_job_signal(int jobid,
 
        job->needs_fence.signaled = true;
        PTHREAD_TEVENT_JOB_THREAD_FENCE(job);
+       if (job->needs_fence.exit_thread) {
+               /*
+                * A problem with the wrapper the current job/worker
+                * thread needs to terminate.
+                *
+                * The pthreadpool_tevent is already gone.
+                */
+               return -1;
+       }
        return 0;
 }
 
index ff2ab7c..6c939fc 100644 (file)
@@ -29,6 +29,38 @@ struct pthreadpool_tevent;
 int pthreadpool_tevent_init(TALLOC_CTX *mem_ctx, unsigned max_threads,
                            struct pthreadpool_tevent **presult);
 
+struct pthreadpool_tevent_wrapper_ops {
+       const char *name;
+
+       bool (*before_job)(struct pthreadpool_tevent *wrap_tp,
+                          void *private_state,
+                          struct pthreadpool_tevent *main_tp,
+                          const char *location);
+       bool (*after_job)(struct pthreadpool_tevent *wrap_tp,
+                         void *private_state,
+                         struct pthreadpool_tevent *main_tp,
+                         const char *location);
+};
+
+struct pthreadpool_tevent *_pthreadpool_tevent_wrapper_create(
+                               struct pthreadpool_tevent *main_tp,
+                               TALLOC_CTX *mem_ctx,
+                               const struct pthreadpool_tevent_wrapper_ops *ops,
+                               void *pstate,
+                               size_t psize,
+                               const char *type,
+                               const char *location);
+#define pthreadpool_tevent_wrapper_create(main_tp, mem_ctx, ops, state, type) \
+       _pthreadpool_tevent_wrapper_create(main_tp, mem_ctx, ops, \
+                                      state, sizeof(type), #type, __location__)
+
+/*
+ * this can only be called directly after
+ * pthreadpool_tevent_wrapper_create()
+ */
+void pthreadpool_tevent_force_per_thread_cwd(struct pthreadpool_tevent *pool,
+                                            const void *private_state);
+
 size_t pthreadpool_tevent_max_threads(struct pthreadpool_tevent *pool);
 size_t pthreadpool_tevent_queued_jobs(struct pthreadpool_tevent *pool);
 bool pthreadpool_tevent_per_thread_cwd(struct pthreadpool_tevent *pool);