svn commit: r238928 - in head/sys: fs/fifofs kern sys

[David Xu]

Author: davidxu
Date: Tue Jul 31 02:00:37 2012
New Revision: 238928
URL: http://svn.freebsd.org/changeset/base/238928

Log:
  When a thread is blocked in direct write state, it only sets PIPE_DIRECTW
  flag but not PIPE_WANTW, but FIFO pipe code does not understand this internal
  state, when a FIFO peer reader closes the pipe, it wants to notify the writer,
  it checks PIPE_WANTW, if not set, it skips calling wakeup(), so blocked writer
  never noticed the case, but in general, the writer should return from the
  syscall with EPIPE error code and may get SIGPIPE signal. Setting the
  PIPE_WANTW fixed problem, or you can turn off direct write, it should fix the
  problem too. This bug is found by PR/170203.
  
  Another bug in FIFO pipe code is when peer closes the pipe, another end which
  is being blocked in select() or poll() is not notified, it missed to call
  pipeselwakeup().
  
  Third problem is found in poll regression test, the existing code can not
  pass 6b,6c,6d tests, but FreeBSD-4 works. This commit does not fix the
  problem, I still need to study more to find the cause.
  
  PR: 170203
  Tested by: Garrett Copper < yanegomi at gmail dot com >

Modified:
  head/sys/fs/fifofs/fifo_vnops.c
  head/sys/kern/sys_pipe.c
  head/sys/sys/pipe.h

Modified: head/sys/fs/fifofs/fifo_vnops.c
==============================================================================
--- head/sys/fs/fifofs/fifo_vnops.c	Tue Jul 31 00:46:19 2012	(r238927)
+++ head/sys/fs/fifofs/fifo_vnops.c	Tue Jul 31 02:00:37 2012	(r238928)
@@ -283,8 +283,11 @@ fifo_close(ap)
 		if (fip->fi_readers == 0) {
 			PIPE_LOCK(cpipe);
 			cpipe->pipe_state |= PIPE_EOF;
-			if (cpipe->pipe_state & PIPE_WANTW)
+			if ((cpipe->pipe_state & PIPE_WANTW)) {
+				cpipe->pipe_state &= ~PIPE_WANTW;
 				wakeup(cpipe);
+			}
+			pipeselwakeup(cpipe);
 			PIPE_UNLOCK(cpipe);
 		}
 	}
@@ -293,10 +296,13 @@ fifo_close(ap)
 		if (fip->fi_writers == 0) {
 			PIPE_LOCK(cpipe);
 			cpipe->pipe_state |= PIPE_EOF;
-			if (cpipe->pipe_state & PIPE_WANTR)
+			if ((cpipe->pipe_state & PIPE_WANTR)) {
+				cpipe->pipe_state &= ~PIPE_WANTR;
 				wakeup(cpipe);
+			}
 			fip->fi_wgen++;
 			FIFO_UPDWGEN(fip, cpipe);
+			pipeselwakeup(cpipe);
 			PIPE_UNLOCK(cpipe);
 		}
 	}

Modified: head/sys/kern/sys_pipe.c
==============================================================================
--- head/sys/kern/sys_pipe.c	Tue Jul 31 00:46:19 2012	(r238927)
+++ head/sys/kern/sys_pipe.c	Tue Jul 31 02:00:37 2012	(r238928)
@@ -227,7 +227,6 @@ static int pipe_create(struct pipe *pipe
 static int pipe_paircreate(struct thread *td, struct pipepair **p_pp);
 static __inline int pipelock(struct pipe *cpipe, int catch);
 static __inline void pipeunlock(struct pipe *cpipe);
-static __inline void pipeselwakeup(struct pipe *cpipe);
 #ifndef PIPE_NODIRECT
 static int pipe_build_write_buffer(struct pipe *wpipe, struct uio *uio);
 static void pipe_destroy_write_buffer(struct pipe *wpipe);
@@ -607,7 +606,7 @@ pipeunlock(cpipe)
 	}
 }
 
-static __inline void
+void
 pipeselwakeup(cpipe)
 	struct pipe *cpipe;
 {
@@ -738,7 +737,7 @@ pipe_read(fp, uio, active_cred, flags, t
 			rpipe->pipe_map.pos += size;
 			rpipe->pipe_map.cnt -= size;
 			if (rpipe->pipe_map.cnt == 0) {
-				rpipe->pipe_state &= ~PIPE_DIRECTW;
+				rpipe->pipe_state &= ~(PIPE_DIRECTW|PIPE_WANTW);
 				wakeup(rpipe);
 			}
 #endif
@@ -1001,6 +1000,7 @@ retry:
 			wakeup(wpipe);
 		}
 		pipeselwakeup(wpipe);
+		wpipe->pipe_state |= PIPE_WANTW;
 		pipeunlock(wpipe);
 		error = msleep(wpipe, PIPE_MTX(wpipe), PRIBIO | PCATCH,
 		    "pipdwt", 0);

Modified: head/sys/sys/pipe.h
==============================================================================
--- head/sys/sys/pipe.h	Tue Jul 31 00:46:19 2012	(r238927)
+++ head/sys/sys/pipe.h	Tue Jul 31 02:00:37 2012	(r238928)
@@ -143,5 +143,5 @@ struct pipepair {
 
 void	pipe_dtor(struct pipe *dpipe);
 int	pipe_named_ctor(struct pipe **ppipe, struct thread *td);
-
+void	pipeselwakeup(struct pipe *cpipe);
 #endif /* !_SYS_PIPE_H_ */