From 75f6325ee25c0ef28fbf3fb77bc71c3f72f8e26f Mon Sep 17 00:00:00 2001
From: J Reece Wilson <me@reece.sx>
Date: Mon, 5 Aug 2024 04:32:52 +0100
Subject: [PATCH] [*] Linux: fix spinning in an io_submit=EAGAIN loop

---
 Source/IO/FS/Async.Linux.cpp      |  4 +++
 Source/IO/UNIX/IOSubmit.Linux.cpp | 55 ++++++++++++++++++++++++++++---
 2 files changed, 54 insertions(+), 5 deletions(-)

diff --git a/Source/IO/FS/Async.Linux.cpp b/Source/IO/FS/Async.Linux.cpp
index 3c8c13d7..97d8c57d 100644
--- a/Source/IO/FS/Async.Linux.cpp
+++ b/Source/IO/FS/Async.Linux.cpp
@@ -609,6 +609,10 @@ namespace Aurora::IO::FS
         }
         else
         {
+            if (!this->pCompletionGroup_ && !this->loopSource_)
+            {
+                this->loopSource_ = AuMakeShared<LinuxAsyncFileTransactionLoopSource>(AuSharedFromThis());
+            }
             return AuStaticCast<Loop::ILoopSource>(AuStaticCast<Loop::ILSEvent>(this->loopSource_));
         }
     }
diff --git a/Source/IO/UNIX/IOSubmit.Linux.cpp b/Source/IO/UNIX/IOSubmit.Linux.cpp
index 25a4a218..55c3b4b6 100644
--- a/Source/IO/UNIX/IOSubmit.Linux.cpp
+++ b/Source/IO/UNIX/IOSubmit.Linux.cpp
@@ -263,6 +263,14 @@ namespace Aurora::IO::UNIX
     // GLUE
     //////////////////////////////////////////////////////////////////
 
+    static void HandleEAGAIN()
+    {
+        // DO NOT
+        LinuxOverlappedYield();
+        // CHANGE!
+        sched_yield();
+    }
+
     static bool LinuxOverlappedTrySubmitWorkInternal(TLSIO *io)
     {
         int index {};
@@ -270,7 +278,16 @@ namespace Aurora::IO::UNIX
 
         while (index != startingLength)
         {
-            int ret = io_submit(io->context, io->submitPendingArray.size() - index, io->submitPendingArray.data() + index);
+            int ret;
+            do
+            {
+                ret = io_submit(io->context, io->submitPendingArray.size() - index, io->submitPendingArray.data() + index);
+                if (ret == -EAGAIN)
+                {
+                    HandleEAGAIN();
+                }
+            }
+            while (ret == -EAGAIN);
 
             if (ret <= 0)
             {
@@ -377,6 +394,7 @@ namespace Aurora::IO::UNIX
         context->abortContext = io->context;
 
         iocb &submit = context->GetIOCB();
+        AuMemset(&submit, 0, sizeof(submit));
         submit.aio_data = context->GetData();
         submit.aio_lio_opcode = op;
         submit.aio_reqprio = 0;
@@ -694,6 +712,7 @@ namespace Aurora::IO::UNIX
         // evil nested epoll garbage
         // but i'm sure the kevent way would be more inefficient
         iocb pollSubmit {};
+        AuMemset(&pollSubmit, 0, sizeof(pollSubmit));
         pollSubmit.aio_fildes = epfd;
         pollSubmit.aio_lio_opcode = IOCB_CMD_POLL;
         pollSubmit.aio_buf = POLLIN;
@@ -701,9 +720,21 @@ namespace Aurora::IO::UNIX
         iocb * ptr = &pollSubmit;
         iocb ** ptrArray = &ptr;
 
-        if (io_submit(io->context, 1, ptrArray) <= 0)
+        errno = 0;
+
+        int error;
+        do
+        {
+            error = io_submit(io->context, 1, ptrArray);
+            if (error == -EAGAIN)
+            {
+                HandleEAGAIN();
+            }
+        }
+        while (error == -EAGAIN);
+
+        if (error <= 0)
         {
-            errno = EFAULT;
             SysPushErrorIO();
             return -1;
         }
@@ -797,7 +828,7 @@ namespace Aurora::IO::UNIX
         io_event finalEpollEvent {};
         if (!bEpollTriggered)
         {
-            if (io_cancel(io->context, ptr, &finalEpollEvent) != 0)
+            if (io_cancel(io->context, &pollSubmit, &finalEpollEvent) != 0)
             {
                 if (errno != EINPROGRESS)
                 {
@@ -864,6 +895,9 @@ namespace Aurora::IO::UNIX
         iocb submit {};
         iocb readSubmit {};
         iocb writeSubmit {};
+        AuMemset(&readSubmit, 0, sizeof(readSubmit));
+        AuMemset(&writeSubmit, 0, sizeof(readSubmit));
+        AuMemset(&submit, 0, sizeof(submit));
         submit.aio_lio_opcode = IOCB_CMD_POLL;
 
         iocb * ptrArray[2];
@@ -887,7 +921,18 @@ namespace Aurora::IO::UNIX
             ptrArray[iocbIdx++] = &writeSubmit;
         }
 
-        if (io_submit(io->context, iocbIdx, ptrArray) <= 0)
+        int error;
+        do
+        {
+            error = io_submit(io->context, iocbIdx, ptrArray);
+            if (error == -EAGAIN)
+            {
+                HandleEAGAIN();
+            }
+        }
+        while (error == -EAGAIN);
+
+        if (error <= 0)
         {
             errno = EFAULT;
             SysPushErrorIO();