Switch KM_SLEEP to KM_PUSHPAGE

Under certain circumstances the following functions may be called
in a context where KM_SLEEP is unsafe and can result in a deadlocked
system.  To avoid this problem the unconditional KM_SLEEPs are
converted to KM_PUSHPAGEs.  This will prevent them from attempting
to initiate any I/O during direct reclaim.

Signed-off-by: Brian Behlendorf <[email protected]>

3 files changed, 6 insertions, 7 deletions

diff --git a/include/sys/taskq.h b/include/sys/taskq.h
index a5d9492f2..a73f7703f 100644
--- a/include/sys/taskq.h
+++ b/include/sys/taskq.h
@@ -62,6 +62,7 @@ typedef struct taskq_ent {
  */
 #define TQ_SLEEP                KM_SLEEP
 #define TQ_NOSLEEP              KM_NOSLEEP
+#define TQ_PUSHPAGE             KM_PUSHPAGE
 #define TQ_NOQUEUE              0x01000000
 #define TQ_NOALLOC              0x02000000
 #define TQ_NEW                  0x04000000
diff --git a/module/spl/spl-taskq.c b/module/spl/spl-taskq.c
index e4092b842..b58eb8e94 100644
--- a/module/spl/spl-taskq.c
+++ b/module/spl/spl-taskq.c
@@ -50,8 +50,6 @@ task_alloc(taskq_t *tq, uint_t flags)
         SENTRY;
 
         ASSERT(tq);
-        ASSERT(flags & (TQ_SLEEP | TQ_NOSLEEP));               /* One set */
-        ASSERT(!((flags & TQ_SLEEP) && (flags & TQ_NOSLEEP))); /* Not both */
         ASSERT(spin_is_locked(&tq->tq_lock));
 retry:
         /* Acquire taskq_ent_t's from free list if available */
@@ -554,7 +552,7 @@ __taskq_create(const char *name, int nthreads, pri_t pri,
 		nthreads = MAX((num_online_cpus() * nthreads) / 100, 1);
 	}
 
-        tq = kmem_alloc(sizeof(*tq), KM_SLEEP);
+        tq = kmem_alloc(sizeof(*tq), KM_PUSHPAGE);
         if (tq == NULL)
                 SRETURN(NULL);
 
@@ -580,12 +578,12 @@ __taskq_create(const char *name, int nthreads, pri_t pri,
 
         if (flags & TASKQ_PREPOPULATE)
                 for (i = 0; i < minalloc; i++)
-                        task_done(tq, task_alloc(tq, TQ_SLEEP | TQ_NEW));
+                        task_done(tq, task_alloc(tq, TQ_PUSHPAGE | TQ_NEW));
 
         spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags);
 
 	for (i = 0; i < nthreads; i++) {
-		tqt = kmem_alloc(sizeof(*tqt), KM_SLEEP);
+		tqt = kmem_alloc(sizeof(*tqt), KM_PUSHPAGE);
 		INIT_LIST_HEAD(&tqt->tqt_thread_list);
 		INIT_LIST_HEAD(&tqt->tqt_active_list);
 		tqt->tqt_tq = tq;
diff --git a/module/spl/spl-thread.c b/module/spl/spl-thread.c
index 9f6e22379..71e5f331d 100644
--- a/module/spl/spl-thread.c
+++ b/module/spl/spl-thread.c
@@ -98,14 +98,14 @@ __thread_create(caddr_t stk, size_t  stksize, thread_func_t func,
 	/* Variable stack size unsupported */
 	ASSERT(stk == NULL);
 
-	tp = kmem_alloc(sizeof(thread_priv_t), KM_SLEEP);
+	tp = kmem_alloc(sizeof(thread_priv_t), KM_PUSHPAGE);
 	if (tp == NULL)
 		SRETURN(NULL);
 
 	tp->tp_magic = TP_MAGIC;
 	tp->tp_name_size = strlen(name) + 1;
 
-	tp->tp_name = kmem_alloc(tp->tp_name_size, KM_SLEEP);
+	tp->tp_name = kmem_alloc(tp->tp_name_size, KM_PUSHPAGE);
         if (tp->tp_name == NULL) {
 		kmem_free(tp, sizeof(thread_priv_t));
 		SRETURN(NULL);