On 10/25/21 7:07 AM, Stefan Hajnoczi wrote:
Compiler optimizations can cache TLS values across coroutine yield
points, resulting in stale values from the previous thread when a
coroutine is re-entered by a new thread.
...
include/qemu/tls.h | 142 +++++++++++++++++++++++++++++++++++++++++++++
Better as qemu/coroutine-tls.h, since it is needed for no other purpose.
+#define QEMU_DEFINE_TLS(type, var) \
+ __thread type qemu_tls_##var; \
+ type get_##var(void) { return qemu_tls_##var; } \
+ void set_##var(type v) { qemu_tls_##var = v; }
You might as well make the variable static, since it may only be referenced by these two
functions.
+#define QEMU_DEFINE_STATIC_TLS(type, var) \
+ static __thread type qemu_tls_##var; \
+ static __attribute__((noinline)) type get_##var(void); \
+ static type get_##var(void) { return qemu_tls_##var; } \
+ static __attribute__((noinline)) void set_##var(type v); \
+ static void set_##var(type v) { qemu_tls_##var = v; }
You don't need separate function declarations; you can fold them together.
If would be nice to inline this when possible,
#if defined(__aarch64__)
#define QEMU_COROUTINE_TLS_ADDR(RET, VAR) \
asm volatile("mrs %0, tpidr_el0\n\t" \
"add %0, %0, #:tprel_hi12:"#VAR", lsl #12\n\t" \
"add %0, %0, #:tprel_lo12_nc:"#VAR \
: "=r"(RET))
#elif defined(__powerpc64__)
#define QEMU_COROUTINE_TLS_ADDR(RET, VAR) \
asm volatile("addis %0,13,"#VAR"@tprel@ha\n\t" \
"add %0,%0,"#VAR"@tprel@l" \
: "=r"(RET))
#elif defined(__riscv)
#define QEMU_COROUTINE_TLS_ADDR(RET, VAR) \
asm volatile("lui %0,%%tprel_hi("#VAR")\n\t" \
"add %0,%0,%%tprel_add("#VAR")\n\t" \
"addi %0,%0,%%tprel_lo("#VAR")" \
: "=r"(RET))
#elif defined(__x86_64__)
#define QEMU_COROUTINE_TLS_ADDR(RET, VAR) \
asm volatile("mov %%fs:"#VAR"@tpoff, %0" : "=r"(RET))
#endif
#ifdef QEMU_COROUTINE_TLS_ADDR
#define QEMU_COROUTINE_TLS_DECLARE(TYPE, VAR) \
extern __thread TYPE co_tls_##VAR; \
static inline TYPE get_##VAR(void) \
{ TYPE *p; QEMU_COROUTINE_TLS_ADDR(p, co_tls_##VAR); return *p; } \
static inline void set_##VAR(TYPE v) \
{ TYPE *p; QEMU_COROUTINE_TLS_ADDR(p, co_tls_##VAR); *p = v; }
#else
etc
#endif
r~
