From 9f87502b4619b60779ce19c41ea0e6bd6582e8e4 Mon Sep 17 00:00:00 2001
From: Fabricio Voznika <fvoznika@google.com>
Date: Thu, 9 Apr 2020 16:40:12 -0700
Subject: Remove TODOs from Async IO

Block and drain requests in io_destroy(2).
Note the reason to create read-only mapping.

PiperOrigin-RevId: 305786312
---
 pkg/sentry/syscalls/linux/sys_aio.go | 34 ++++++++++++++++++++++++++--------
 1 file changed, 26 insertions(+), 8 deletions(-)

(limited to 'pkg/sentry/syscalls/linux')

diff --git a/pkg/sentry/syscalls/linux/sys_aio.go b/pkg/sentry/syscalls/linux/sys_aio.go
index b401978db..38cbeba5a 100644
--- a/pkg/sentry/syscalls/linux/sys_aio.go
+++ b/pkg/sentry/syscalls/linux/sys_aio.go
@@ -114,14 +114,28 @@ func IoSetup(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysca
 func IoDestroy(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
 	id := args[0].Uint64()
 
-	// Destroy the given context.
-	if !t.MemoryManager().DestroyAIOContext(t, id) {
+	ctx := t.MemoryManager().DestroyAIOContext(t, id)
+	if ctx == nil {
 		// Does not exist.
 		return 0, nil, syserror.EINVAL
 	}
-	// FIXME(fvoznika): Linux blocks until all AIO to the destroyed context is
-	// done.
-	return 0, nil, nil
+
+	// Drain completed requests amd wait for pending requests until there are no
+	// more.
+	for {
+		ctx.Drain()
+
+		ch := ctx.WaitChannel()
+		if ch == nil {
+			// No more requests, we're done.
+			return 0, nil, nil
+		}
+		// The task cannot be interrupted during the wait. Equivalent to
+		// TASK_UNINTERRUPTIBLE in Linux.
+		t.UninterruptibleSleepStart(true /* deactivate */)
+		<-ch
+		t.UninterruptibleSleepFinish(true /* activate */)
+	}
 }
 
 // IoGetevents implements linux syscall io_getevents(2).
@@ -200,13 +214,13 @@ func IoGetevents(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.S
 func waitForRequest(ctx *mm.AIOContext, t *kernel.Task, haveDeadline bool, deadline ktime.Time) (interface{}, error) {
 	for {
 		if v, ok := ctx.PopRequest(); ok {
-			// Request was readly available. Just return it.
+			// Request was readily available. Just return it.
 			return v, nil
 		}
 
 		// Need to wait for request completion.
-		done, active := ctx.WaitChannel()
-		if !active {
+		done := ctx.WaitChannel()
+		if done == nil {
 			// Context has been destroyed.
 			return nil, syserror.EINVAL
 		}
@@ -248,6 +262,10 @@ func memoryFor(t *kernel.Task, cb *ioCallback) (usermem.IOSequence, error) {
 }
 
 func performCallback(t *kernel.Task, file *fs.File, cbAddr usermem.Addr, cb *ioCallback, ioseq usermem.IOSequence, ctx *mm.AIOContext, eventFile *fs.File) {
+	if ctx.Dead() {
+		ctx.CancelPendingRequest()
+		return
+	}
 	ev := &ioEvent{
 		Data: cb.Data,
 		Obj:  uint64(cbAddr),
-- 
cgit v1.2.3