sunrpc: add some tracepoints around enqueue and dequeue of svc_xprt

These were useful when I was tracking down a race condition between
svc_xprt_do_enqueue and svc_get_next_xprt.

Signed-off-by: Jeff Layton <jlayton@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

2 files changed, 109 insertions, 7 deletions

diff --git a/include/trace/events/sunrpc.h b/include/trace/events/sunrpc.h
index ee4438a63a48..b9c1dc6c825a 100644
--- a/include/trace/events/sunrpc.h
+++ b/include/trace/events/sunrpc.h
@@ -8,6 +8,7 @@
 #include <linux/sunrpc/clnt.h>
 #include <linux/sunrpc/svc.h>
 #include <linux/sunrpc/xprtsock.h>
+#include <linux/sunrpc/svc_xprt.h>
 #include <net/tcp_states.h>
 #include <linux/net.h>
 #include <linux/tracepoint.h>
@@ -480,6 +481,99 @@ DEFINE_EVENT(svc_rqst_status, svc_send,
         TP_PROTO(struct svc_rqst *rqst, int status),
         TP_ARGS(rqst, status));
 
+#define show_svc_xprt_flags(flags)                                      \
+        __print_flags(flags, "|",                                       \
+                { (1UL << XPT_BUSY),            "XPT_BUSY"},            \
+                { (1UL << XPT_CONN),            "XPT_CONN"},            \
+                { (1UL << XPT_CLOSE),           "XPT_CLOSE"},           \
+                { (1UL << XPT_DATA),            "XPT_DATA"},            \
+                { (1UL << XPT_TEMP),            "XPT_TEMP"},            \
+                { (1UL << XPT_DEAD),            "XPT_DEAD"},            \
+                { (1UL << XPT_CHNGBUF),         "XPT_CHNGBUF"},         \
+                { (1UL << XPT_DEFERRED),        "XPT_DEFERRED"},        \
+                { (1UL << XPT_OLD),             "XPT_OLD"},             \
+                { (1UL << XPT_LISTENER),        "XPT_LISTENER"},        \
+                { (1UL << XPT_CACHE_AUTH),      "XPT_CACHE_AUTH"},      \
+                { (1UL << XPT_LOCAL),           "XPT_LOCAL"})
+
+TRACE_EVENT(svc_xprt_do_enqueue,
+        TP_PROTO(struct svc_xprt *xprt, struct svc_rqst *rqst),
+
+        TP_ARGS(xprt, rqst),
+
+        TP_STRUCT__entry(
+                __field(struct svc_xprt *, xprt)
+                __field(struct svc_rqst *, rqst)
+        ),
+
+        TP_fast_assign(
+                __entry->xprt = xprt;
+                __entry->rqst = rqst;
+        ),
+
+        TP_printk("xprt=0x%p addr=%pIScp pid=%d flags=%s", __entry->xprt,
+                (struct sockaddr *)&__entry->xprt->xpt_remote,
+                __entry->rqst ? __entry->rqst->rq_task->pid : 0,
+                show_svc_xprt_flags(__entry->xprt->xpt_flags))
+);
+
+TRACE_EVENT(svc_xprt_dequeue,
+        TP_PROTO(struct svc_xprt *xprt),
+
+        TP_ARGS(xprt),
+
+        TP_STRUCT__entry(
+                __field(struct svc_xprt *, xprt)
+                __field_struct(struct sockaddr_storage, ss)
+                __field(unsigned long, flags)
+        ),
+
+        TP_fast_assign(
+                __entry->xprt = xprt,
+                xprt ? memcpy(&__entry->ss, &xprt->xpt_remote, sizeof(__entry->ss)) : memset(&__entry->ss, 0, sizeof(__entry->ss));
+                __entry->flags = xprt ? xprt->xpt_flags : 0;
+        ),
+
+        TP_printk("xprt=0x%p addr=%pIScp flags=%s", __entry->xprt,
+                (struct sockaddr *)&__entry->ss,
+                show_svc_xprt_flags(__entry->flags))
+);
+
+TRACE_EVENT(svc_wake_up,
+        TP_PROTO(int pid),
+
+        TP_ARGS(pid),
+
+        TP_STRUCT__entry(
+                __field(int, pid)
+        ),
+
+        TP_fast_assign(
+                __entry->pid = pid;
+        ),
+
+        TP_printk("pid=%d", __entry->pid)
+);
+
+TRACE_EVENT(svc_handle_xprt,
+        TP_PROTO(struct svc_xprt *xprt, int len),
+
+        TP_ARGS(xprt, len),
+
+        TP_STRUCT__entry(
+                __field(struct svc_xprt *, xprt)
+                __field(int, len)
+        ),
+
+        TP_fast_assign(
+                __entry->xprt = xprt;
+                __entry->len = len;
+        ),
+
+        TP_printk("xprt=0x%p addr=%pIScp len=%d flags=%s", __entry->xprt,
+                (struct sockaddr *)&__entry->xprt->xpt_remote, __entry->len,
+                show_svc_xprt_flags(__entry->xprt->xpt_flags))
+);
 #endif /* _TRACE_SUNRPC_H */
 
 #include <trace/define_trace.h>
diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
index ed90d955f733..73d40bd1839a 100644
--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -322,12 +322,12 @@ static bool svc_xprt_has_something_to_do(struct svc_xprt *xprt)
 static void svc_xprt_do_enqueue(struct svc_xprt *xprt)
 {
         struct svc_pool *pool;
-        struct svc_rqst *rqstp;
+        struct svc_rqst *rqstp = NULL;
         int cpu;
         bool queued = false;
 
         if (!svc_xprt_has_something_to_do(xprt))
-                return;
+                goto out;
 
         /* Mark transport as busy. It will remain in this state until
          * the provider calls svc_xprt_received. We update XPT_BUSY
@@ -337,7 +337,7 @@ static void svc_xprt_do_enqueue(struct svc_xprt *xprt)
         if (test_and_set_bit(XPT_BUSY, &xprt->xpt_flags)) {
                 /* Don't enqueue transport while already enqueued */
                 dprintk("svc: transport %p busy, not enqueued\n", xprt);
-                return;
+                goto out;
         }
 
         cpu = get_cpu();
@@ -377,7 +377,7 @@ redo_search:
                 atomic_long_inc(&pool->sp_stats.threads_woken);
                 wake_up_process(rqstp->rq_task);
                 put_cpu();
-                return;
+                goto out;
         }
         rcu_read_unlock();
 
@@ -396,7 +396,10 @@ redo_search:
                 spin_unlock_bh(&pool->sp_lock);
                 goto redo_search;
         }
+        rqstp = NULL;
         put_cpu();
+out:
+        trace_svc_xprt_do_enqueue(xprt, rqstp);
 }
 
 /*
@@ -420,7 +423,7 @@ static struct svc_xprt *svc_xprt_dequeue(struct svc_pool *pool)
         struct svc_xprt *xprt = NULL;
 
         if (list_empty(&pool->sp_sockets))
-                return NULL;
+                goto out;
 
         spin_lock_bh(&pool->sp_lock);
         if (likely(!list_empty(&pool->sp_sockets))) {
@@ -433,7 +436,8 @@ static struct svc_xprt *svc_xprt_dequeue(struct svc_pool *pool)
                         xprt, atomic_read(&xprt->xpt_ref.refcount));
         }
         spin_unlock_bh(&pool->sp_lock);
-
+out:
+        trace_svc_xprt_dequeue(xprt);
         return xprt;
 }
 
@@ -515,6 +519,7 @@ void svc_wake_up(struct svc_serv *serv)
                 rcu_read_unlock();
                 dprintk("svc: daemon %p woken up.\n", rqstp);
                 wake_up_process(rqstp->rq_task);
+                trace_svc_wake_up(rqstp->rq_task->pid);
                 return;
         }
         rcu_read_unlock();
@@ -522,6 +527,7 @@ void svc_wake_up(struct svc_serv *serv)
         /* No free entries available */
         set_bit(SP_TASK_PENDING, &pool->sp_flags);
         smp_wmb();
+        trace_svc_wake_up(0);
 }
 EXPORT_SYMBOL_GPL(svc_wake_up);
 
@@ -740,7 +746,7 @@ static int svc_handle_xprt(struct svc_rqst *rqstp, struct svc_xprt *xprt)
                 dprintk("svc_recv: found XPT_CLOSE\n");
                 svc_delete_xprt(xprt);
                 /* Leave XPT_BUSY set on the dead xprt: */
-                return 0;
+                goto out;
         }
         if (test_bit(XPT_LISTENER, &xprt->xpt_flags)) {
                 struct svc_xprt *newxpt;
@@ -771,6 +777,8 @@ static int svc_handle_xprt(struct svc_rqst *rqstp, struct svc_xprt *xprt)
         }
         /* clear XPT_BUSY: */
         svc_xprt_received(xprt);
+out:
+        trace_svc_handle_xprt(xprt, len);
         return len;
 }