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coroutine-ucontext: use QEMU_DEFINE_STATIC_CO_TLS() 

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.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20220307153853.602859-2-stefanha@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2022-03-07 15:38:51 +00:00 committed by Kevin Wolf
parent ecf3200703
commit 34145a307d
1 changed files with 24 additions and 14 deletions
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38
util/coroutine-ucontext.c
View File

@ -25,6 +25,7 @@
#include "qemu/osdep.h"
#include <ucontext.h>
#include "qemu/coroutine_int.h"
#include "qemu/coroutine-tls.h"
#ifdef CONFIG_VALGRIND_H
#include <valgrind/valgrind.h>
@ -66,8 +67,8 @@ typedef struct {
/**
* Per-thread coroutine bookkeeping
*/
static __thread CoroutineUContext leader;
static __thread Coroutine *current;
QEMU_DEFINE_STATIC_CO_TLS(Coroutine *, current);
QEMU_DEFINE_STATIC_CO_TLS(CoroutineUContext, leader);
/*
* va_args to makecontext() must be type 'int', so passing
@ -97,14 +98,15 @@ static inline __attribute__((always_inline))
void finish_switch_fiber(void *fake_stack_save)
{
#ifdef CONFIG_ASAN
CoroutineUContext *leaderp = get_ptr_leader();
const void *bottom_old;
size_t size_old;
__sanitizer_finish_switch_fiber(fake_stack_save, &bottom_old, &size_old);
if (!leader.stack) {
leader.stack = (void *)bottom_old;
leader.stack_size = size_old;
if (!leaderp->stack) {
leaderp->stack = (void *)bottom_old;
leaderp->stack_size = size_old;
}
#endif
#ifdef CONFIG_TSAN
@ -161,8 +163,10 @@ static void coroutine_trampoline(int i0, int i1)
/* Initialize longjmp environment and switch back the caller */
if (!sigsetjmp(self->env, 0)) {
start_switch_fiber_asan(COROUTINE_YIELD, &fake_stack_save, leader.stack,
leader.stack_size);
CoroutineUContext *leaderp = get_ptr_leader();
start_switch_fiber_asan(COROUTINE_YIELD, &fake_stack_save,
leaderp->stack, leaderp->stack_size);
start_switch_fiber_tsan(&fake_stack_save, self, true); /* true=caller */
siglongjmp(*(sigjmp_buf *)co->entry_arg, 1);
}
@ -297,7 +301,7 @@ qemu_coroutine_switch(Coroutine *from_, Coroutine *to_,
int ret;
void *fake_stack_save = NULL;
current = to_;
set_current(to_);
ret = sigsetjmp(from->env, 0);
if (ret == 0) {
@ -315,18 +319,24 @@ qemu_coroutine_switch(Coroutine *from_, Coroutine *to_,
Coroutine *qemu_coroutine_self(void)
{
if (!current) {
current = &leader.base;
Coroutine *self = get_current();
CoroutineUContext *leaderp = get_ptr_leader();
if (!self) {
self = &leaderp->base;
set_current(self);
}
#ifdef CONFIG_TSAN
if (!leader.tsan_co_fiber) {
leader.tsan_co_fiber = __tsan_get_current_fiber();
if (!leaderp->tsan_co_fiber) {
leaderp->tsan_co_fiber = __tsan_get_current_fiber();
}
#endif
return current;
return self;
}
bool qemu_in_coroutine(void)
{
return current && current->caller;
Coroutine *self = get_current();
return self && self->caller;
}