tree 4cb9104cf0a0184d030e7ae5a18b41c8639be213
parent e59c0a09a31fc6adc3bda0d1dc30c01d45fcabf6
author Sabrina Dubroca <sdubroca@redhat.com> 1497365326 +0200
committer Jan Stancek <jstancek@redhat.com> 1497451985 +0200

recvmsg03: avoid close() and recvmsg() racing

This testcase rarely hangs on single CPU systems. Problem
appears to be between recvmsg() and close():
1. sendmsg(), packet gets queued
2. close(), packet is dropped
3. recvmsg(), nothing to fetch

strace of a buggy run:
  [pid 17284] 16:04:41.042617 socket(AF_RDS, SOCK_SEQPACKET, 0) = 3
  [pid 17284] 16:04:41.049549 close(3)    = 0
  strace: Process 17290 attached
  [pid 17284] 16:04:41.050765 socket(AF_RDS, SOCK_SEQPACKET, 0 <unfinished ...>
  [pid 17290] 16:04:41.050894 futex(0x7f95dfc57014, FUTEX_WAIT, 0, {tv_sec=10, tv_nsec=0} <unfinished ...>
  [pid 17284] 16:04:41.051001 <... socket resumed> ) = 3
  [pid 17284] 16:04:41.051111 bind(3, {sa_family=AF_INET, sin_port=htons(4000), sin_addr=inet_addr("127.0.0.1")}, 16) = 0
  [pid 17284] 16:04:41.051374 futex(0x7f95dfc57014, FUTEX_WAKE, 2147483647) = 1
  [pid 17290] 16:04:41.051432 <... futex resumed> ) = 0
  [pid 17284] 16:04:41.051442 recvmsg(3,  <unfinished ...>
  [pid 17290] 16:04:41.051455 socket(AF_RDS, SOCK_SEQPACKET, 0) = 3
  [pid 17290] 16:04:41.051666 bind(3, {sa_family=AF_INET, sin_port=htons(4001), sin_addr=inet_addr("127.0.0.1")}, 16) = 0
  [pid 17290] 16:04:41.051724 sendmsg(3, {msg_name={sa_family=AF_INET, sin_port=htons(4000), sin_addr=inet_addr("127.0.0.1")}, msg_namelen=16, msg_iov=[{iov_base="hello world\0", iov_len=12}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, 0) = 12
  [pid 17290] 16:04:41.051975 close(3)    = 0
  [pid 17290] 16:04:41.052492 +++ exited with 0 +++
  [pid 17284] 16:04:41.052598 <... recvmsg resumed> {msg_namelen=32}, 0) = ? ERESTARTSYS (To be restarted if SA_RESTART is set)
  [pid 17284] 16:04:41.052631 --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=17290, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
  [pid 17284] 16:04:41.052718 recvmsg(3, // hang

Signed-off-by: Sabrina Dubroca <sdubroca@redhat.com>
[ wrote changelog message ]
Acked-by: Jan Stancek <jstancek@redhat.com>
Acked-by: Cyril Hrubis <chrubis@suse.cz>