100 lines
3.4 KiB
Diff
100 lines
3.4 KiB
Diff
From 336581e6e9ace3f1ddd24ad0a258db9785f9b0ed Mon Sep 17 00:00:00 2001
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From: Stefan Hajnoczi <stefanha@redhat.com>
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Date: Tue, 17 May 2022 12:08:12 +0100
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Subject: [PATCH 3/6] coroutine-win32: use QEMU_DEFINE_STATIC_CO_TLS()
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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RH-Author: Stefan Hajnoczi <stefanha@redhat.com>
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RH-MergeRequest: 89: coroutine: use coroutine TLS macros to protect thread-local variables
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RH-Commit: [3/3] 55b35dfdae1bc7d6f614ac9f81a92f5c6431f713 (stefanha/centos-stream-qemu-kvm)
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RH-Bugzilla: 1952483
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RH-Acked-by: Hanna Reitz <hreitz@redhat.com>
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RH-Acked-by: Eric Blake <eblake@redhat.com>
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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Thread-Local Storage variables cannot be used directly from coroutine
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code because the compiler may optimize TLS variable accesses across
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qemu_coroutine_yield() calls. When the coroutine is re-entered from
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another thread the TLS variables from the old thread must no longer be
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used.
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Use QEMU_DEFINE_STATIC_CO_TLS() for the current and leader variables.
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I think coroutine-win32.c could get away with __thread because the
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variables are only used in situations where either the stale value is
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correct (current) or outside coroutine context (loading leader when
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current is NULL). Due to the difficulty of being sure that this is
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really safe in all scenarios it seems worth converting it anyway.
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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Message-Id: <20220307153853.602859-4-stefanha@redhat.com>
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Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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(cherry picked from commit c1fe694357a328c807ae3cc6961c19e923448fcc)
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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---
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util/coroutine-win32.c | 18 +++++++++++++-----
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1 file changed, 13 insertions(+), 5 deletions(-)
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diff --git a/util/coroutine-win32.c b/util/coroutine-win32.c
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index de6bd4fd3e..c02a62c896 100644
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--- a/util/coroutine-win32.c
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+++ b/util/coroutine-win32.c
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@@ -25,6 +25,7 @@
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#include "qemu/osdep.h"
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#include "qemu-common.h"
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#include "qemu/coroutine_int.h"
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+#include "qemu/coroutine-tls.h"
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typedef struct
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{
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@@ -34,8 +35,8 @@ typedef struct
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CoroutineAction action;
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} CoroutineWin32;
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-static __thread CoroutineWin32 leader;
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-static __thread Coroutine *current;
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+QEMU_DEFINE_STATIC_CO_TLS(CoroutineWin32, leader);
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+QEMU_DEFINE_STATIC_CO_TLS(Coroutine *, current);
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/* This function is marked noinline to prevent GCC from inlining it
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* into coroutine_trampoline(). If we allow it to do that then it
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@@ -52,7 +53,7 @@ qemu_coroutine_switch(Coroutine *from_, Coroutine *to_,
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CoroutineWin32 *from = DO_UPCAST(CoroutineWin32, base, from_);
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CoroutineWin32 *to = DO_UPCAST(CoroutineWin32, base, to_);
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- current = to_;
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+ set_current(to_);
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to->action = action;
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SwitchToFiber(to->fiber);
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@@ -89,14 +90,21 @@ void qemu_coroutine_delete(Coroutine *co_)
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Coroutine *qemu_coroutine_self(void)
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{
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+ Coroutine *current = get_current();
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+
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if (!current) {
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- current = &leader.base;
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- leader.fiber = ConvertThreadToFiber(NULL);
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+ CoroutineWin32 *leader = get_ptr_leader();
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+
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+ current = &leader->base;
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+ set_current(current);
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+ leader->fiber = ConvertThreadToFiber(NULL);
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}
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return current;
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}
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bool qemu_in_coroutine(void)
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{
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+ Coroutine *current = get_current();
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+
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return current && current->caller;
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}
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--
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2.31.1
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