c1fe694357
Thread-Local Storage variables cannot be used directly from coroutine code because the compiler may optimize TLS variable accesses across qemu_coroutine_yield() calls. When the coroutine is re-entered from another thread the TLS variables from the old thread must no longer be used. Use QEMU_DEFINE_STATIC_CO_TLS() for the current and leader variables. I think coroutine-win32.c could get away with __thread because the variables are only used in situations where either the stale value is correct (current) or outside coroutine context (loading leader when current is NULL). Due to the difficulty of being sure that this is really safe in all scenarios it seems worth converting it anyway. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Message-Id: <20220307153853.602859-4-stefanha@redhat.com> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
110 lines
3.2 KiB
C
110 lines
3.2 KiB
C
/*
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* Win32 coroutine initialization code
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*
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* Copyright (c) 2011 Kevin Wolf <kwolf@redhat.com>
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#include "qemu/osdep.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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Coroutine base;
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LPVOID fiber;
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CoroutineAction action;
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} CoroutineWin32;
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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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* hoists the code to get the address of the TLS variable "current"
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* out of the while() loop. This is an invalid transformation because
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* the SwitchToFiber() call may be called when running thread A but
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* return in thread B, and so we might be in a different thread
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* context each time round the loop.
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*/
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CoroutineAction __attribute__((noinline))
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qemu_coroutine_switch(Coroutine *from_, Coroutine *to_,
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CoroutineAction action)
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{
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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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set_current(to_);
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to->action = action;
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SwitchToFiber(to->fiber);
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return from->action;
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}
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static void CALLBACK coroutine_trampoline(void *co_)
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{
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Coroutine *co = co_;
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while (true) {
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co->entry(co->entry_arg);
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qemu_coroutine_switch(co, co->caller, COROUTINE_TERMINATE);
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}
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}
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Coroutine *qemu_coroutine_new(void)
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{
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const size_t stack_size = COROUTINE_STACK_SIZE;
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CoroutineWin32 *co;
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co = g_malloc0(sizeof(*co));
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co->fiber = CreateFiber(stack_size, coroutine_trampoline, &co->base);
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return &co->base;
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}
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void qemu_coroutine_delete(Coroutine *co_)
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{
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CoroutineWin32 *co = DO_UPCAST(CoroutineWin32, base, co_);
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DeleteFiber(co->fiber);
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g_free(co);
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}
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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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if (!current) {
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CoroutineWin32 *leader = get_ptr_leader();
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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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return current && current->caller;
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}
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