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coroutine-ucontext: use QEMU_DEFINE_STATIC_CO_TLS()

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