summaryrefslogtreecommitdiffstats
path: root/xlators/features/qemu-block
diff options
context:
space:
mode:
authorBrian Foster <bfoster@redhat.com>2013-10-18 07:36:38 -0400
committerAnand Avati <avati@redhat.com>2013-11-10 23:45:46 -0800
commitb06ecde2997b72a41b2f2d25d55e61d30ea46bc2 (patch)
treeff630d050b46310141d0ca11ee56b04736d06cea /xlators/features/qemu-block
parent0826f9073a93c6d499f3d2077695455854d0fa7f (diff)
features/qemu-block: simplify coroutine model to use single synctask, ucontext
The current coroutine model, mapping synctasks 1-1 with qemu internal Coroutines, has some unresolved raciness issues. This problem usually manifests as lifecycle mismatches between top-level (gluster created) synctasks and the subsequently created internal coroutines from that context. Qemu's internal queueing (and locking) can cause situations where the top-level synctask is destroyed before the internal scheduler has released references to memory, leading to use after free crashes and asserts. Simplify the coroutine model to use a single synctask as a coroutine processor and rely on the existing native ucontext coroutine implementation. The syncenv thread is donated to qemu and ensures a single top-level coroutine is processed at a time. Qemu now has complete control over coroutine scheduling. BUG: 986775 Change-Id: I38223479a608d80353128e390f243933fc946fd6 Signed-off-by: Brian Foster <bfoster@redhat.com> Reviewed-on: http://review.gluster.org/6110 Tested-by: Gluster Build System <jenkins@build.gluster.com> Reviewed-by: Anand Avati <avati@redhat.com>
Diffstat (limited to 'xlators/features/qemu-block')
-rw-r--r--xlators/features/qemu-block/src/Makefile.am2
-rw-r--r--xlators/features/qemu-block/src/coroutine-synctask.c215
-rw-r--r--xlators/features/qemu-block/src/coroutine-synctask.h51
-rw-r--r--xlators/features/qemu-block/src/qb-coroutines.c47
-rw-r--r--xlators/features/qemu-block/src/qb-coroutines.h1
-rw-r--r--xlators/features/qemu-block/src/qemu-block.c1
-rw-r--r--xlators/features/qemu-block/src/qemu-block.h3
7 files changed, 72 insertions, 248 deletions
diff --git a/xlators/features/qemu-block/src/Makefile.am b/xlators/features/qemu-block/src/Makefile.am
index 1a249bb..08a7b62 100644
--- a/xlators/features/qemu-block/src/Makefile.am
+++ b/xlators/features/qemu-block/src/Makefile.am
@@ -9,6 +9,7 @@ qemu_block_la_SOURCES_qemu = \
$(CONTRIBDIR)/qemu/qemu-coroutine.c \
$(CONTRIBDIR)/qemu/qemu-coroutine-lock.c \
$(CONTRIBDIR)/qemu/qemu-coroutine-sleep.c \
+ $(CONTRIBDIR)/qemu/coroutine-ucontext.c \
$(CONTRIBDIR)/qemu/block.c \
$(CONTRIBDIR)/qemu/nop-symbols.c
@@ -140,7 +141,6 @@ noinst_HEADERS = \
$(noinst_HEADERS_qemu) \
qemu-block.h \
qemu-block-memory-types.h \
- coroutine-synctask.h \
qb-coroutines.h
AM_CPPFLAGS = $(GF_CPPFLAGS) -I$(top_srcdir)/libglusterfs/src \
diff --git a/xlators/features/qemu-block/src/coroutine-synctask.c b/xlators/features/qemu-block/src/coroutine-synctask.c
index c3538f6..e43988a 100644
--- a/xlators/features/qemu-block/src/coroutine-synctask.c
+++ b/xlators/features/qemu-block/src/coroutine-synctask.c
@@ -22,192 +22,95 @@
#include "qemu-block-memory-types.h"
#include "qemu-block.h"
-#include "coroutine-synctask.h"
-void
-qemu_coroutine_delete (Coroutine *co_)
-{
- struct synctask *synctask = NULL;
- CoroutineSynctask *cs = NULL;
-
- cs = DO_UPCAST(CoroutineSynctask, base, co_);
- synctask = cs->synctask;
-
- cs->die = 1;
- synctask_wake (synctask);
-
- /* Do not free either @cs or @synctask here.
- @synctask is naturally destroyed when
- cs_proc() returns (after "break"ing out of
- the loop because of setting cs->die=1 above.
-
- We free @cs too just before returning from
- cs_proc()
- */
- return;
-}
-
-
-CoroutineAction
-qemu_coroutine_switch (Coroutine *from_, Coroutine *to_, CoroutineAction action)
+/*
+ * This code serves as the bridge from the main glusterfs context to the qemu
+ * coroutine context via synctask. We create a single threaded syncenv with a
+ * single synctask responsible for processing a queue of coroutines. The qemu
+ * code invoked from within the synctask function handlers uses the ucontext
+ * coroutine implementation and scheduling logic internal to qemu. This
+ * effectively donates a thread of execution to qemu and its internal coroutine
+ * management.
+ *
+ * NOTE: The existence of concurrent synctasks has proven quite racy with regard
+ * to qemu coroutine management, particularly related to the lifecycle
+ * differences with top-level synctasks and internally created coroutines and
+ * interactions with qemu-internal queues (and locks, in turn). We explicitly
+ * disallow this scenario, via the queue, until it is more well supported.
+ */
+
+static struct {
+ struct list_head queue;
+ gf_lock_t lock;
+ struct synctask *task;
+} qb_co;
+
+static void
+init_qbco()
{
- struct synctask *to = NULL;
- struct synctask *from = NULL;
- CoroutineSynctask *csto = NULL;
- CoroutineSynctask *csfrom = NULL;
-
- csto = DO_UPCAST(CoroutineSynctask, base, to_);
- csfrom = DO_UPCAST(CoroutineSynctask, base, from_);
- to = csto->synctask;
- from = csfrom->synctask;
-
- /* TODO: need mutex/cond guarding when making syncenv
- multithreaded
- */
- csfrom->run = false;
- csto->run = true;
-
- /* the next three lines must be in this specific order only */
- csfrom->action = action;
-
- synctask_wake (to);
-
- synctask_yield (from);
-
- /* the yielder set @action value in @csfrom, but for the
- resumer it is @csto
- */
- return csto->action;
+ INIT_LIST_HEAD(&qb_co.queue);
+ LOCK_INIT(&qb_co.lock);
}
-
-int
-cs_fin (int ret, call_frame_t *frame, void *opaque)
+static int
+synctask_nop_cbk (int ret, call_frame_t *frame, void *opaque)
{
- /* nop */
return 0;
}
-
static int
-cs_proc (void *opaque)
+qb_synctask_wrap (void *opaque)
{
- CoroutineSynctask *cs = opaque;
- struct synctask *synctask = NULL;
-
- synctask = synctask_get (); /* == cs->synctask */
+ qb_local_t *qb_local, *tmp;
- for (;;) {
- while (!cs->run && !cs->die)
- /* entry function (i.e cs->base.entry) will
- not be set just yet first time. Wait for
- caller to set it and call switch()
- */
- synctask_yield (synctask);
+ LOCK(&qb_co.lock);
- if (cs->die)
+ while (!list_empty(&qb_co.queue)) {
+ list_for_each_entry_safe(qb_local, tmp, &qb_co.queue, list) {
+ list_del_init(&qb_local->list);
break;
+ }
- cs->base.entry (cs->base.entry_arg);
- qemu_coroutine_switch (&cs->base, cs->base.caller,
- COROUTINE_TERMINATE);
- }
-
- GF_FREE (cs);
-
- return 0;
-}
-
-
-Coroutine *
-qemu_coroutine_new()
-{
- qb_conf_t *conf = NULL;
- CoroutineSynctask *cs = NULL;
- struct synctask *task = NULL;
-
- conf = THIS->private;
-
- cs = GF_CALLOC (1, sizeof (*cs), gf_qb_mt_coroutinesynctask_t);
- if (!cs)
- return NULL;
-
- task = synctask_get ();
- /* Inherit the frame from the parent synctask, as this will
- carry forward things like uid, gid, pid, lkowner etc. of the
- caller properly.
- */
- cs->synctask = synctask_create (conf->env, cs_proc, cs_fin,
- task ? task->frame : NULL, cs);
- if (!cs->synctask)
- return NULL;
-
- return &cs->base;
-}
-
+ UNLOCK(&qb_co.lock);
-Coroutine *
-qemu_coroutine_self()
-{
- struct synctask *synctask = NULL;
- CoroutineSynctask *cs = NULL;
-
- synctask = synctask_get();
-
- cs = synctask->opaque;
-
- return &cs->base;
-}
-
-
-bool
-qemu_in_coroutine ()
-{
- Coroutine *co = NULL;
+ qb_local->synctask_fn(qb_local);
+ /* qb_local is now unwound and gone! */
- co = qemu_coroutine_self ();
-
- return co && co->caller;
-}
+ LOCK(&qb_co.lock);
+ }
+ qb_co.task = NULL;
-/* These are calls for the "top" xlator to invoke/submit
- coroutines
-*/
+ UNLOCK(&qb_co.lock);
-static int
-synctask_nop_cbk (int ret, call_frame_t *frame, void *opaque)
-{
return 0;
}
-
-int
-qb_synctask_wrap (void *opaque)
-{
- struct synctask *task = NULL;
- CoroutineSynctask *cs = NULL;
- qb_local_t *qb_local = NULL;
-
- task = synctask_get ();
- cs = opaque;
- cs->synctask = task;
- qb_local = DO_UPCAST (qb_local_t, cs, cs);
-
- return qb_local->synctask_fn (opaque);
-}
-
-
int
qb_coroutine (call_frame_t *frame, synctask_fn_t fn)
{
qb_local_t *qb_local = NULL;
qb_conf_t *qb_conf = NULL;
+ static int init = 0;
qb_local = frame->local;
qb_local->synctask_fn = fn;
qb_conf = frame->this->private;
- return synctask_new (qb_conf->env, qb_synctask_wrap, synctask_nop_cbk,
- frame, &qb_local->cs);
+ if (!init) {
+ init = 1;
+ init_qbco();
+ }
+
+ LOCK(&qb_co.lock);
+
+ if (!qb_co.task)
+ qb_co.task = synctask_create(qb_conf->env, qb_synctask_wrap,
+ synctask_nop_cbk, frame, NULL);
+
+ list_add_tail(&qb_local->list, &qb_co.queue);
+
+ UNLOCK(&qb_co.lock);
+
+ return 0;
}
diff --git a/xlators/features/qemu-block/src/coroutine-synctask.h b/xlators/features/qemu-block/src/coroutine-synctask.h
deleted file mode 100644
index 0f0aa99..0000000
--- a/xlators/features/qemu-block/src/coroutine-synctask.h
+++ /dev/null
@@ -1,51 +0,0 @@
-/*
- Copyright (c) 2013 Red Hat, Inc. <http://www.redhat.com>
- This file is part of GlusterFS.
-
- This file is licensed to you under your choice of the GNU Lesser
- General Public License, version 3 or any later version (LGPLv3 or
- later), or the GNU General Public License, version 2 (GPLv2), in all
- cases as published by the Free Software Foundation.
-*/
-
-#ifndef __COROUTINE_SYNCTASK_H
-#define __COROUTINE_SYNCTASK_H
-
-#include "syncop.h"
-#include "block/coroutine_int.h"
-#include "qemu-common.h"
-#include "block/coroutine_int.h"
-
-/*
- Three entities:
-
- synctask - glusterfs implementation of xlator friendly lightweight threads
- Coroutine - qemu coroutine API for its block drivers
- CoroutineSynctask - implementation of Coroutine using synctasks
-
- Coroutine is an "embedded" structure inside CoroutineSynctask, called "base".
-
- E.g:
-
- Coroutine *co;
- CoroutineSynctask *cs;
- struct synctask *synctask;
-
- cs == synctask->opaque;
- co == &(cs->base);
- cs = DO_UPCAST(CoroutineSynctask, base, co);
- synctask == cs->synctask;
-
-*/
-
-typedef struct {
- Coroutine base;
- struct synctask *synctask;
- CoroutineAction action;
- bool run;
- bool die;
-} CoroutineSynctask;
-
-
-
-#endif /* !__COROUTINE_SYNCTASK_H */
diff --git a/xlators/features/qemu-block/src/qb-coroutines.c b/xlators/features/qemu-block/src/qb-coroutines.c
index d29117e..7c52adb 100644
--- a/xlators/features/qemu-block/src/qb-coroutines.c
+++ b/xlators/features/qemu-block/src/qb-coroutines.c
@@ -29,7 +29,6 @@
int
qb_format_and_resume (void *opaque)
{
- CoroutineSynctask *cs = NULL;
qb_local_t *local = NULL;
call_frame_t *frame = NULL;
call_stub_t *stub = NULL;
@@ -44,9 +43,7 @@ qb_format_and_resume (void *opaque)
qb_conf_t *qb_conf = NULL;
int ret = -1;
- cs = opaque;
-
- local = DO_UPCAST(qb_local_t, cs, cs);
+ local = opaque;
frame = local->frame;
stub = local->stub;
inode = local->inode;
@@ -224,16 +221,13 @@ err:
int
qb_co_open (void *opaque)
{
- CoroutineSynctask *cs = NULL;
qb_local_t *local = NULL;
call_frame_t *frame = NULL;
call_stub_t *stub = NULL;
inode_t *inode = NULL;
qb_inode_t *qb_inode = NULL;
- cs = opaque;
-
- local = DO_UPCAST(qb_local_t, cs, cs);
+ local = opaque;
frame = local->frame;
stub = local->stub;
inode = local->inode;
@@ -262,7 +256,6 @@ qb_co_open (void *opaque)
int
qb_co_writev (void *opaque)
{
- CoroutineSynctask *cs = NULL;
qb_local_t *local = NULL;
call_frame_t *frame = NULL;
call_stub_t *stub = NULL;
@@ -271,9 +264,7 @@ qb_co_writev (void *opaque)
QEMUIOVector qiov = {0, };
int ret = 0;
- cs = opaque;
-
- local = DO_UPCAST(qb_local_t, cs, cs);
+ local = opaque;
frame = local->frame;
stub = local->stub;
inode = local->inode;
@@ -309,7 +300,6 @@ qb_co_writev (void *opaque)
int
qb_co_readv (void *opaque)
{
- CoroutineSynctask *cs = NULL;
qb_local_t *local = NULL;
call_frame_t *frame = NULL;
call_stub_t *stub = NULL;
@@ -320,9 +310,7 @@ qb_co_readv (void *opaque)
struct iovec iov = {0, };
int ret = 0;
- cs = opaque;
-
- local = DO_UPCAST(qb_local_t, cs, cs);
+ local = opaque;
frame = local->frame;
stub = local->stub;
inode = local->inode;
@@ -391,7 +379,6 @@ qb_co_readv (void *opaque)
int
qb_co_fsync (void *opaque)
{
- CoroutineSynctask *cs = NULL;
qb_local_t *local = NULL;
call_frame_t *frame = NULL;
call_stub_t *stub = NULL;
@@ -399,9 +386,7 @@ qb_co_fsync (void *opaque)
qb_inode_t *qb_inode = NULL;
int ret = 0;
- cs = opaque;
-
- local = DO_UPCAST(qb_local_t, cs, cs);
+ local = opaque;
frame = local->frame;
stub = local->stub;
inode = local->inode;
@@ -461,7 +446,6 @@ qb_update_size_xattr (xlator_t *this, fd_t *fd, const char *fmt, off_t offset)
int
qb_co_truncate (void *opaque)
{
- CoroutineSynctask *cs = NULL;
qb_local_t *local = NULL;
call_frame_t *frame = NULL;
call_stub_t *stub = NULL;
@@ -472,9 +456,8 @@ qb_co_truncate (void *opaque)
xlator_t *this = NULL;
this = THIS;
- cs = opaque;
- local = DO_UPCAST(qb_local_t, cs, cs);
+ local = opaque;
frame = local->frame;
stub = local->stub;
inode = local->inode;
@@ -523,14 +506,13 @@ out:
int
qb_co_close (void *opaque)
{
- CoroutineSynctask *cs = NULL;
qb_local_t *local = NULL;
call_frame_t *frame = NULL;
inode_t *inode = NULL;
qb_inode_t *qb_inode = NULL;
BlockDriverState *bs = NULL;
- local = DO_UPCAST(qb_local_t, cs, cs);
+ local = opaque;
inode = local->inode;
qb_inode = qb_inode_ctx_get (THIS, inode);
@@ -553,7 +535,6 @@ qb_co_close (void *opaque)
int
qb_snapshot_create (void *opaque)
{
- CoroutineSynctask *cs = NULL;
qb_local_t *local = NULL;
call_frame_t *frame = NULL;
call_stub_t *stub = NULL;
@@ -563,9 +544,7 @@ qb_snapshot_create (void *opaque)
struct timeval tv = {0, };
int ret = 0;
- cs = opaque;
-
- local = DO_UPCAST(qb_local_t, cs, cs);
+ local = opaque;
frame = local->frame;
stub = local->stub;
inode = local->inode;
@@ -604,7 +583,6 @@ qb_snapshot_create (void *opaque)
int
qb_snapshot_delete (void *opaque)
{
- CoroutineSynctask *cs = NULL;
qb_local_t *local = NULL;
call_frame_t *frame = NULL;
call_stub_t *stub = NULL;
@@ -612,9 +590,7 @@ qb_snapshot_delete (void *opaque)
qb_inode_t *qb_inode = NULL;
int ret = 0;
- cs = opaque;
-
- local = DO_UPCAST(qb_local_t, cs, cs);
+ local = opaque;
frame = local->frame;
stub = local->stub;
inode = local->inode;
@@ -648,7 +624,6 @@ qb_snapshot_delete (void *opaque)
int
qb_snapshot_goto (void *opaque)
{
- CoroutineSynctask *cs = NULL;
qb_local_t *local = NULL;
call_frame_t *frame = NULL;
call_stub_t *stub = NULL;
@@ -656,9 +631,7 @@ qb_snapshot_goto (void *opaque)
qb_inode_t *qb_inode = NULL;
int ret = 0;
- cs = opaque;
-
- local = DO_UPCAST(qb_local_t, cs, cs);
+ local = opaque;
frame = local->frame;
stub = local->stub;
inode = local->inode;
diff --git a/xlators/features/qemu-block/src/qb-coroutines.h b/xlators/features/qemu-block/src/qb-coroutines.h
index 6707d6d..583319f 100644
--- a/xlators/features/qemu-block/src/qb-coroutines.h
+++ b/xlators/features/qemu-block/src/qb-coroutines.h
@@ -15,7 +15,6 @@
#include "call-stub.h"
#include "block/block_int.h"
#include "monitor/monitor.h"
-#include "coroutine-synctask.h"
int qb_format_and_resume (void *opaque);
int qb_snapshot_create (void *opaque);
diff --git a/xlators/features/qemu-block/src/qemu-block.c b/xlators/features/qemu-block/src/qemu-block.c
index 0edb7b9..48bbf31 100644
--- a/xlators/features/qemu-block/src/qemu-block.c
+++ b/xlators/features/qemu-block/src/qemu-block.c
@@ -204,6 +204,7 @@ qb_local_init (call_frame_t *frame)
qb_local = GF_CALLOC (1, sizeof (*qb_local), gf_qb_mt_qb_local_t);
if (!qb_local)
return -1;
+ INIT_LIST_HEAD(&qb_local->list);
qb_local->frame = frame;
frame->local = qb_local;
diff --git a/xlators/features/qemu-block/src/qemu-block.h b/xlators/features/qemu-block/src/qemu-block.h
index 55e7c23..c95f279 100644
--- a/xlators/features/qemu-block/src/qemu-block.h
+++ b/xlators/features/qemu-block/src/qemu-block.h
@@ -15,7 +15,6 @@
#include "call-stub.h"
#include "block/block_int.h"
#include "monitor/monitor.h"
-#include "coroutine-synctask.h"
/* QB_XATTR_KEY_FMT is the on-disk xattr stored in the inode which
indicates that the file must be "interpreted" by the block format
@@ -59,7 +58,6 @@ typedef struct qb_conf {
typedef struct qb_local {
- CoroutineSynctask cs;
call_frame_t *frame; /* backpointer */
call_stub_t *stub;
inode_t *inode;
@@ -67,6 +65,7 @@ typedef struct qb_local {
char fmt[QB_XATTR_VAL_MAX+1];
char name[256];
synctask_fn_t synctask_fn;
+ struct list_head list;
} qb_local_t;
void qb_local_free (xlator_t *this, qb_local_t *local);