netdev - [PATCH v2] net: tracepoint: fix print wrong sysctl

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Date:   Tue,  8 Sep 2020 10:09:39 +0800
From:   Dust Li <dust.li@...ux.alibaba.com>
To:     Jakub Kicinski <kuba@...nel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Satoru Moriya <satoru.moriya@....com>
Cc:     netdev@...r.kernel.org
Subject: [PATCH v2] net: tracepoint: fix print wrong sysctl_mem value

sysctl_mem is an point, and tracepoint entry do not support
been visited like an array. Use an __array(3) to store sysctl_mem
instead.

tracpoint output with and without this fix:
- without fix:
   28821.074 sock:sock_exceed_buf_limit:proto:UDP
   sysctl_mem=-1741233440,19,322156906942464 allocated=19 sysctl_rmem=4096
   rmem_alloc=75008 sysctl_wmem=4096 wmem_alloc=1 wmem_queued=0
   kind=SK_MEM_RECV

- with fix:
  2126.136 sock:sock_exceed_buf_limit:proto:UDP
  sysctl_mem=18,122845,184266 allocated=19 sysctl_rmem=4096
  rmem_alloc=73728 sysctl_wmem=4096 wmem_alloc=1 wmem_queued=0
  kind=SK_MEM_RECV

v2: use __array(3) instead of 3 long type to store sysctl_mem

Fixes: 3847ce32aea9fdf ("core: add tracepoints for queueing skb to rcvbuf")
Signed-off-by: Dust Li <dust.li@...ux.alibaba.com>
---
 include/trace/events/sock.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/trace/events/sock.h b/include/trace/events/sock.h
index a966d4b5ab37..914e58938480 100644
--- a/include/trace/events/sock.h
+++ b/include/trace/events/sock.h
@@ -98,7 +98,7 @@ TRACE_EVENT(sock_exceed_buf_limit,
 
 	TP_STRUCT__entry(
 		__array(char, name, 32)
-		__field(long *, sysctl_mem)
+		__array(long, sysctl_mem, 3)
 		__field(long, allocated)
 		__field(int, sysctl_rmem)
 		__field(int, rmem_alloc)
@@ -110,7 +110,9 @@ TRACE_EVENT(sock_exceed_buf_limit,
 
 	TP_fast_assign(
 		strncpy(__entry->name, prot->name, 32);
-		__entry->sysctl_mem = prot->sysctl_mem;
+		__entry->sysctl_mem[0] = prot->sysctl_mem[0];
+		__entry->sysctl_mem[1] = prot->sysctl_mem[1];
+		__entry->sysctl_mem[2] = prot->sysctl_mem[2];
 		__entry->allocated = allocated;
 		__entry->sysctl_rmem = sk_get_rmem0(sk, prot);
 		__entry->rmem_alloc = atomic_read(&sk->sk_rmem_alloc);
-- 
2.19.1.3.ge56e4f7