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From 5946a6ec18976c0f52162fe0f47e9b5171af87ec Mon Sep 17 00:00:00 2001
From: Soumya Koduri <skoduri@redhat.com>
Date: Mon, 6 Apr 2020 12:36:44 +0530
Subject: [PATCH 503/511] gfapi: Suspend synctasks instead of blocking them
There are certain conditions which blocks the current
execution thread (like waiting on mutex lock or condition
variable or I/O response). In such cases, if it is a
synctask thread, we should suspend the task instead
of blocking it (like done in SYNCOP using synctask_yield)
This is to avoid deadlock like the one mentioned below -
1) synctaskA sets fs->migration_in_progress to 1 and
does I/O (LOOKUP)
2) Other synctask threads wait for fs->migration_in_progress
to be reset to 0 by synctaskA and hence blocked
3) but synctaskA cannot resume as all synctask threads are blocked
on (2).
Note: this same approach is already used by few other components
like syncbarrier etc.
>Change-Id: If90f870d663bb242c702a5b86ac52eeda67c6f0d
>Fixes: #1146
>Signed-off-by: Soumya Koduri <skoduri@redhat.com>
Upstream patch: https://review.gluster.org/c/glusterfs/+/24276
BUG: 1779238
Change-Id: If90f870d663bb242c702a5b86ac52eeda67c6f0d
Signed-off-by: nik-redhat <nladha@redhat.com>
Reviewed-on: https://code.engineering.redhat.com/gerrit/221081
Tested-by: RHGS Build Bot <nigelb@redhat.com>
Reviewed-by: Soumya Koduri <skoduri@redhat.com>
---
api/src/glfs-internal.h | 34 ++++++++++++++++++++++++++++++++--
api/src/glfs-resolve.c | 9 +++++++++
api/src/glfs.c | 9 +++++++++
3 files changed, 50 insertions(+), 2 deletions(-)
diff --git a/api/src/glfs-internal.h b/api/src/glfs-internal.h
index 55401b2..15cf0ee 100644
--- a/api/src/glfs-internal.h
+++ b/api/src/glfs-internal.h
@@ -16,6 +16,7 @@
#include <glusterfs/upcall-utils.h>
#include "glfs-handles.h"
#include <glusterfs/refcount.h>
+#include <glusterfs/syncop.h>
#define GLFS_SYMLINK_MAX_FOLLOW 2048
@@ -207,6 +208,7 @@ struct glfs {
glfs_upcall_cbk up_cbk; /* upcall cbk function to be registered */
void *up_data; /* Opaque data provided by application
* during upcall registration */
+ struct list_head waitq; /* waiting synctasks */
};
/* This enum is used to maintain the state of glfd. In case of async fops
@@ -442,6 +444,34 @@ glfs_process_upcall_event(struct glfs *fs, void *data)
THIS = glfd->fd->inode->table->xl->ctx->master; \
} while (0)
+#define __GLFS_LOCK_WAIT(fs) \
+ do { \
+ struct synctask *task = NULL; \
+ \
+ task = synctask_get(); \
+ \
+ if (task) { \
+ list_add_tail(&task->waitq, &fs->waitq); \
+ pthread_mutex_unlock(&fs->mutex); \
+ synctask_yield(task, NULL); \
+ pthread_mutex_lock(&fs->mutex); \
+ } else { \
+ /* non-synctask */ \
+ pthread_cond_wait(&fs->cond, &fs->mutex); \
+ } \
+ } while (0)
+
+#define __GLFS_SYNCTASK_WAKE(fs) \
+ do { \
+ struct synctask *waittask = NULL; \
+ \
+ while (!list_empty(&fs->waitq)) { \
+ waittask = list_entry(fs->waitq.next, struct synctask, waitq); \
+ list_del_init(&waittask->waitq); \
+ synctask_wake(waittask); \
+ } \
+ } while (0)
+
/*
By default all lock attempts from user context must
use glfs_lock() and glfs_unlock(). This allows
@@ -466,10 +496,10 @@ glfs_lock(struct glfs *fs, gf_boolean_t wait_for_migration)
pthread_mutex_lock(&fs->mutex);
while (!fs->init)
- pthread_cond_wait(&fs->cond, &fs->mutex);
+ __GLFS_LOCK_WAIT(fs);
while (wait_for_migration && fs->migration_in_progress)
- pthread_cond_wait(&fs->cond, &fs->mutex);
+ __GLFS_LOCK_WAIT(fs);
return 0;
}
diff --git a/api/src/glfs-resolve.c b/api/src/glfs-resolve.c
index 062b7dc..58b6ace 100644
--- a/api/src/glfs-resolve.c
+++ b/api/src/glfs-resolve.c
@@ -65,6 +65,9 @@ __glfs_first_lookup(struct glfs *fs, xlator_t *subvol)
fs->migration_in_progress = 0;
pthread_cond_broadcast(&fs->cond);
+ /* wake up other waiting tasks */
+ __GLFS_SYNCTASK_WAKE(fs);
+
return ret;
}
@@ -154,6 +157,9 @@ __glfs_refresh_inode(struct glfs *fs, xlator_t *subvol, inode_t *inode,
fs->migration_in_progress = 0;
pthread_cond_broadcast(&fs->cond);
+ /* wake up other waiting tasks */
+ __GLFS_SYNCTASK_WAKE(fs);
+
return newinode;
}
@@ -841,6 +847,9 @@ __glfs_migrate_fd(struct glfs *fs, xlator_t *newsubvol, struct glfs_fd *glfd)
fs->migration_in_progress = 0;
pthread_cond_broadcast(&fs->cond);
+ /* wake up other waiting tasks */
+ __GLFS_SYNCTASK_WAKE(fs);
+
return newfd;
}
diff --git a/api/src/glfs.c b/api/src/glfs.c
index f36616d..ae994fa 100644
--- a/api/src/glfs.c
+++ b/api/src/glfs.c
@@ -740,6 +740,7 @@ glfs_new_fs(const char *volname)
INIT_LIST_HEAD(&fs->openfds);
INIT_LIST_HEAD(&fs->upcall_list);
+ INIT_LIST_HEAD(&fs->waitq);
PTHREAD_MUTEX_INIT(&fs->mutex, NULL, fs->pthread_flags, GLFS_INIT_MUTEX,
err);
@@ -1228,6 +1229,7 @@ pub_glfs_fini(struct glfs *fs)
call_pool_t *call_pool = NULL;
int fs_init = 0;
int err = -1;
+ struct synctask *waittask = NULL;
DECLARE_OLD_THIS;
@@ -1249,6 +1251,13 @@ pub_glfs_fini(struct glfs *fs)
call_pool = fs->ctx->pool;
+ /* Wake up any suspended synctasks */
+ while (!list_empty(&fs->waitq)) {
+ waittask = list_entry(fs->waitq.next, struct synctask, waitq);
+ list_del_init(&waittask->waitq);
+ synctask_wake(waittask);
+ }
+
while (countdown--) {
/* give some time for background frames to finish */
pthread_mutex_lock(&fs->mutex);
--
1.8.3.1
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