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sunrpc: add some tracepoints around enqueue and dequeue of svc_xprt
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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>
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Jeff Layton authored and J. Bruce Fields committed Dec 9, 2014
1 parent b1691bc commit 83a712e
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Showing 2 changed files with 109 additions and 7 deletions.
94 changes: 94 additions & 0 deletions include/trace/events/sunrpc.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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>
Expand Down Expand Up @@ -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>
22 changes: 15 additions & 7 deletions net/sunrpc/svc_xprt.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand All @@ -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();
Expand Down Expand Up @@ -377,7 +377,7 @@ static void svc_xprt_do_enqueue(struct svc_xprt *xprt)
atomic_long_inc(&pool->sp_stats.threads_woken);
wake_up_process(rqstp->rq_task);
put_cpu();
return;
goto out;
}
rcu_read_unlock();

Expand All @@ -396,7 +396,10 @@ static void svc_xprt_do_enqueue(struct svc_xprt *xprt)
spin_unlock_bh(&pool->sp_lock);
goto redo_search;
}
rqstp = NULL;
put_cpu();
out:
trace_svc_xprt_do_enqueue(xprt, rqstp);
}

/*
Expand All @@ -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))) {
Expand All @@ -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;
}

Expand Down Expand Up @@ -515,13 +519,15 @@ 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();

/* 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);

Expand Down Expand 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;
Expand Down Expand Up @@ -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;
}

Expand Down

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