iscsi-target: Fix connection reset hang with percpu_ida_alloc

Nicholas Bellinger · Nicholas Bellinger · commit 555b270e25b0 · 2014-01-25T06:58:52.000Z
This patch addresses a bug where connection reset would hang
indefinately once percpu_ida_alloc() was starved for tags, due
to the fact that it always assumed uninterruptible sleep mode.

So now make percpu_ida_alloc() check for signal_pending_state() for
making interruptible sleep optional, and convert iscsit_allocate_cmd()
to set TASK_INTERRUPTIBLE for GFP_KERNEL, or TASK_RUNNING for
GFP_ATOMIC.

Reported-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Cc: Kent Overstreet &lt;kmo@daterainc.com&gt;
Cc: &lt;stable@vger.kernel.org&gt; #3.12+
Signed-off-by: Nicholas Bellinger &lt;nab@linux-iscsi.org&gt;
diff --git a/drivers/target/iscsi/iscsi_target_util.c b/drivers/target/iscsi/iscsi_target_util.c
@@ -156,7 +156,7 @@ struct iscsi_cmd *iscsit_allocate_cmd(struct iscsi_conn *conn, gfp_t gfp_mask)
 {
 	struct iscsi_cmd *cmd;
 	struct se_session *se_sess = conn->sess->se_sess;
-	int size, tag, state = (gfp_mask & __GFP_WAIT) ? TASK_UNINTERRUPTIBLE :
+	int size, tag, state = (gfp_mask & __GFP_WAIT) ? TASK_INTERRUPTIBLE :
 				TASK_RUNNING;
 
 	tag = percpu_ida_alloc(&se_sess->sess_tag_pool, state);
diff --git a/lib/percpu_ida.c b/lib/percpu_ida.c
@@ -138,14 +138,14 @@ static inline unsigned alloc_local_tag(struct percpu_ida_cpu *tags)
  * tag_pool_init()), or otherwise -ENOSPC on allocation failure.
  *
  * Safe to be called from interrupt context (assuming it isn't passed
- * TASK_UNINTERRUPTIBLE, of course).
+ * TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE, of course).
  *
  * @gfp indicates whether or not to wait until a free id is available (it's not
  * used for internal memory allocations); thus if passed __GFP_WAIT we may sleep
  * however long it takes until another thread frees an id (same semantics as a
  * mempool).
  *
- * Will not fail if passed TASK_UNINTERRUPTIBLE.
+ * Will not fail if passed TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE.
  */
 int percpu_ida_alloc(struct percpu_ida *pool, int state)
 {
@@ -195,6 +195,11 @@ int percpu_ida_alloc(struct percpu_ida *pool, int state)
 		if (tag >= 0 || state == TASK_RUNNING)
 			break;
 
+		if (signal_pending_state(state, current)) {
+			tag = -ERESTARTSYS;
+			break;
+		}
+
 		schedule();
 
 		local_irq_save(flags);

Original file line number	Diff line number	Diff line change
`@@ -156,7 +156,7 @@ struct iscsi_cmd iscsit_allocate_cmd(struct iscsi_conn conn, gfp_t gfp_mask)`
`156`	`156`	`{`
`157`	`157`	`struct iscsi_cmd *cmd;`
`158`	`158`	`struct se_session *se_sess = conn->sess->se_sess;`
`159`		`- int size, tag, state = (gfp_mask & __GFP_WAIT) ? TASK_UNINTERRUPTIBLE :`
	`159`	`+ int size, tag, state = (gfp_mask & __GFP_WAIT) ? TASK_INTERRUPTIBLE :`
`160`	`160`	`TASK_RUNNING;`
`161`	`161`
`162`	`162`	`tag = percpu_ida_alloc(&se_sess->sess_tag_pool, state);`