From c23f711243fe29605c0655f099eee9733e73cb27 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Henrik=20Grubbstr=C3=B6m=20=28Grubba=29?=
<grubba@grubba.org>
Date: Thu, 8 May 2014 16:17:32 +0200
Subject: [PATCH] Backend: unhook_fd_callback_box() now also unlinks.
Active fd boxes that were destructed could potentially have their
next link zapped, which would break the cyclic list and drop the
following fd boxes on the floor, and not having them get added to
the active fd_list any more.
Potential fix for backend stopping notifications on some long time
fds, and starting to eat 100% cpu.
---
src/backend.cmod | 55 +++++++++++++++++++++++++++++++++++++-----------
src/backend.h | 7 ++++--
2 files changed, 48 insertions(+), 14 deletions(-)
diff --git a/src/backend.cmod b/src/backend.cmod
index db05aa48fd..56e10ca98a 100644
--- a/src/backend.cmod
+++ b/src/backend.cmod
@@ -1676,6 +1676,26 @@ PIKECLASS Backend
if (box->ref_obj && box->events) add_ref (box->ref_obj);
}
+ /**
+ * Unlink the box from the active list it is on (if any),
+ * and return 1 if it was active (and thus needs to be freed).
+ */
+ static int unlink_box(struct fd_callback_box *box)
+ {
+ if (box->next) {
+ /* The box is active in some backend. Unlink it. */
+ struct fd_callback_box *pred = box->next;
+ /* Find the predecessor. */
+ while (pred->next != box) {
+ pred = pred->next;
+ }
+ pred->next = box->next;
+ box->next = NULL;
+ return 1;
+ }
+ return 0;
+ }
+
PMOD_EXPORT void unhook_fd_callback_box (struct fd_callback_box *box)
{
/* Accept an unhooked box; can happen when we're called from an
@@ -1696,6 +1716,20 @@ PIKECLASS Backend
/* Make sure no further callbacks are called on this box. */
box->revents = 0;
box->rflags = 0;
+
+ /* Unlink the box from the active list in case it is there,
+ * otherwise the active list may get cut, which could cause
+ * the remaining boxes on the list to be lost from the backend..
+ */
+ if (unlink_box(box) && box->ref_obj) {
+ /* Use gc safe method to allow calls from within the gc. */
+ /* box->ref_obj is only converted from a counted to
+ * non-counted ref, so it shouldn't be clobbered by the free. */
+ union anything u;
+ u.object = box->ref_obj;
+ gc_free_short_svalue (&u, T_OBJECT);
+ }
+
if (box->ref_obj && box->events) {
/* Use gc safe method to allow calls from within the gc. */
/* box->ref_obj is only converted from a counted to
@@ -1703,6 +1737,7 @@ PIKECLASS Backend
union anything u;
u.object = box->ref_obj;
gc_free_short_svalue (&u, T_OBJECT);
+ box->events = 0;
}
}
@@ -1752,16 +1787,12 @@ PIKECLASS Backend
if (old) {
if (box->fd >= 0) update_fd_set (old, box->fd, box->events, 0, box->flags);
remove_fd_box (box);
- if (box->next) {
- /* The box is active in the old backend. Unlink it. */
- struct fd_callback_box *pred = box->next;
- /* Find the predecessor. */
- while (pred->next != box) {
- pred = pred->next;
- }
- pred->next = box->next;
- box->next = NULL;
- if (box->ref_obj) free_object(box->ref_obj);
+
+ /* Unlink the box from the active in the old backend,
+ * and free it if it was there.
+ */
+ if (unlink_box(box) && box->ref_obj) {
+ free_object(box->ref_obj);
}
}
box->backend = new;
@@ -1795,7 +1826,7 @@ PIKECLASS Backend
add_fd_box (box);
new_fd = box->fd;
box->revents = 0;
- box->rflags = 0;
+ box->rflags = 0;
if (new_fd >= 0) update_fd_set (box->backend, new_fd, 0, box->events, box->flags);
}
@@ -2221,7 +2252,7 @@ PIKECLASS Backend
}
box->revents = 0;
- box->rflags = 0;
+ box->rflags = 0;
/* We don't want to keep this fd anymore.
* Note: This disables any further callbacks.
diff --git a/src/backend.h b/src/backend.h
index 7841bba00c..54f2c49110 100644
--- a/src/backend.h
+++ b/src/backend.h
@@ -119,10 +119,13 @@ struct fd_callback_box
struct object *ref_obj; /**< If set, it's the object containing the box.
* It then acts as the ref from the backend to
* the object and is refcounted by the backend
- * whenever any event is wanted. */
+ * whenever any event is wanted.
+ *
+ * It receives a ref for each when next and/or
+ * events are non-zero. */
struct fd_callback_box *next; /**< Circular list of active fds in a backend.
* NULL if the fd is not active in some
- * backend. Note: ref_obj MUST be freed if
+ * backend. Note: ref_obj MUST be freed when
* the box is unlinked. */
int fd; /**< Use change_fd_for_box to change this. May
* be negative, in which case only the ref
--
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