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3db1859b48c133fc21db9a7045a59c29db59cd76 [patch]

ed18778a717286b9c82e8abf268ba711cfcba208

24f5f6a6bebefadaf51b1f15211fecb350c52ed4

3db1859b48c133fc21db9a7045a59c29db59cd76.tar.gz

kernel/fifo: honor O_NONBLOCK on open() for FIFOs

according to POSIX:
- O_NONBLOCK set:
	* read-only open() shall return asap
	* write-only open() shall return an error if no reader.
- O_NONBLOCK clear:
	* read-only open() shall block until a writer opens.
	* write-only open() shall block until a reader opens.

for FIFOs used for pipes, open with O_NONBLOCK then reset O_NONBLOCK.

can be tested with:
bash -norc -c '/bin/printf "test" > >(/bin/tee -a trace.log) 2>&1'

Change-Id: I3cb70810fec50f643b5e6e84dbdeb0a16961936a
Reviewed-on: https://review.haiku-os.org/c/haiku/+/8469
Reviewed-by: waddlesplash <waddlesplash@gmail.com>
Reviewed-on: https://review.haiku-os.org/c/haiku/+/8506

Diff

 src/system/kernel/fs/fifo.cpp | 46 ++++++++++++++++++++++++++++++++++++++--------
 src/system/kernel/fs/vfs.cpp  |  6 ++++--
 2 files changed, 40 insertions(+), 12 deletions(-)

diff --git a/src/system/kernel/fs/fifo.cpp b/src/system/kernel/fs/fifo.cpp
index 02441b8..d557df9 100644
--- a/src/system/kernel/fs/fifo.cpp
+++ b/src/system/kernel/fs/fifo.cpp
@@ -185,7 +185,7 @@
			void				NotifyBytesWritten(size_t bytes);
			void				NotifyEndClosed(bool writer);

			void				Open(int openMode);
			status_t			Open(int openMode);
			void				Close(file_cookie* cookie);
			int32				ReaderCount() const { return fReaderCount; }
			int32				WriterCount() const { return fWriterCount; }
@@ -209,7 +209,7 @@

			mutex				fRequestLock;

			ConditionVariable	fWriteCondition;
			ConditionVariable	fActiveCondition;

			int32				fReaderCount;
			int32				fWriterCount;
@@ -352,7 +352,7 @@
	fReadSelectSyncPool(NULL),
	fWriteSelectSyncPool(NULL)
{
	fWriteCondition.Publish(this, "pipe");
	fActiveCondition.Publish(this, "pipe");
	mutex_init(&fRequestLock, "pipe request");

	bigtime_t time = real_time_clock();
@@ -364,7 +364,7 @@

Inode::~Inode()
{
	fWriteCondition.Unpublish();
	fActiveCondition.Unpublish();
	mutex_destroy(&fRequestLock);
}

@@ -566,7 +566,7 @@
			size_t minWriteCount = request->MinimalWriteCount();
			if (minWriteCount > 0 && minWriteCount <= writable
					&& minWriteCount > writable - bytes) {
				fWriteCondition.NotifyAll();
				fActiveCondition.NotifyAll();
				break;
			}
		}
@@ -620,7 +620,7 @@
		}
	} else {
		// Last reader is gone. Wake up all writers.
		fWriteCondition.NotifyAll();
		fActiveCondition.NotifyAll();

		if (fWriteSelectSyncPool)
			notify_select_event_pool(fWriteSelectSyncPool, B_SELECT_ERROR);
@@ -628,7 +628,7 @@
}


void
status_t
Inode::Open(int openMode)
{
	MutexLocker locker(RequestLock());
@@ -638,6 +638,27 @@

	if ((openMode & O_ACCMODE) == O_RDONLY || (openMode & O_ACCMODE) == O_RDWR)
		fReaderCount++;

	bool shouldWait = false;
	if ((openMode & O_ACCMODE) == O_WRONLY && fReaderCount == 0) {
		if ((openMode & O_NONBLOCK) != 0)
			return ENXIO;
		shouldWait = true;
	}
	if ((openMode & O_ACCMODE) == O_RDONLY && fWriterCount == 0
		&& (openMode & O_NONBLOCK) == 0) {
		shouldWait = true;
	}
	if (shouldWait) {
		// prepare for waiting for the condition variable.
		ConditionVariableEntry waitEntry;
		fActiveCondition.Add(&waitEntry);
		locker.Unlock();
		status_t status = waitEntry.Wait(B_CAN_INTERRUPT);
		if (status != B_OK)
			return status;
		locker.Lock();
	}

	if (fReaderCount > 0 && fWriterCount > 0) {
		TRACE("Inode %p::Open(): fifo becomes active\n", this);
@@ -647,8 +668,9 @@
		// notify all waiting writers that they can start
		if (fWriteSelectSyncPool)
			notify_select_event_pool(fWriteSelectSyncPool, B_SELECT_WRITE);
		fWriteCondition.NotifyAll();
		fActiveCondition.NotifyAll();
	}
	return B_OK;
}


@@ -682,7 +704,7 @@
		// Notify any still reading writers to stop
		// TODO: This only works reliable if there is only one writer - we could
		// do the same thing done for the read requests.
		fWriteCondition.NotifyAll(B_FILE_ERROR);
		fActiveCondition.NotifyAll(B_FILE_ERROR);
	}

	if (fReaderCount == 0 && fWriterCount == 0) {
@@ -888,7 +910,11 @@

	TRACE("  open cookie = %p\n", cookie);
	cookie->open_mode = openMode;
	inode->Open(openMode);
	status_t status = inode->Open(openMode);
	if (status != B_OK) {
		free(cookie);
		return status;
	}

	*_cookie = (void*)cookie;

diff --git a/src/system/kernel/fs/vfs.cpp b/src/system/kernel/fs/vfs.cpp
index 25aafae..9414fa2 100644
--- a/src/system/kernel/fs/vfs.cpp
+++ b/src/system/kernel/fs/vfs.cpp
@@ -9605,10 +9605,12 @@
	}

	// Everything looks good so far. Open two FDs for reading respectively
	// writing.
	// writing, O_NONBLOCK to avoid blocking on open with O_RDONLY
	int fds[2];
	fds[0] = open_vnode(vnode, O_RDONLY, false);
	fds[0] = open_vnode(vnode, O_RDONLY | O_NONBLOCK, false);
	fds[1] = open_vnode(vnode, O_WRONLY, false);
	// Reset O_NONBLOCK
	_kern_fcntl(fds[0], F_SETFL, 0);

	FDCloser closer0(fds[0], false);
	FDCloser closer1(fds[1], false);