From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56979) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZCSso-0005fQ-W7 for qemu-devel@nongnu.org; Tue, 07 Jul 2015 09:26:00 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZCSsl-0004XG-NX for qemu-devel@nongnu.org; Tue, 07 Jul 2015 09:25:58 -0400 Received: from greensocs.com ([193.104.36.180]:52522) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZCSsl-0004Wp-2t for qemu-devel@nongnu.org; Tue, 07 Jul 2015 09:25:55 -0400 Message-ID: <559BD35E.7050309@greensocs.com> Date: Tue, 07 Jul 2015 15:25:50 +0200 From: Frederic Konrad MIME-Version: 1.0 References: <1435330053-18733-1-git-send-email-fred.konrad@greensocs.com> <1435330053-18733-9-git-send-email-fred.konrad@greensocs.com> <87lhes9l0l.fsf@linaro.org> In-Reply-To: <87lhes9l0l.fsf@linaro.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [RFC PATCH V6 08/18] cpu: remove exit_request global. List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: =?UTF-8?B?QWxleCBCZW5uw6ll?= Cc: mttcg@listserver.greensocs.com, peter.maydell@linaro.org, a.spyridakis@virtualopensystems.com, mark.burton@greensocs.com, agraf@suse.de, qemu-devel@nongnu.org, guillaume.delbergue@greensocs.com, pbonzini@redhat.com, alistair.francis@xilinx.com On 07/07/2015 15:04, Alex Benn=C3=A9e wrote: > fred.konrad@greensocs.com writes: > >> From: KONRAD Frederic >> >> This removes exit_request global and adds a variable in CPUState for t= his. >> Only the flag for the first cpu is used for the moment as we are still= with one >> TCG thread. >> >> Signed-off-by: KONRAD Frederic >> --- >> cpu-exec.c | 15 --------------- >> cpus.c | 17 ++++++++++++++--- >> 2 files changed, 14 insertions(+), 18 deletions(-) >> >> diff --git a/cpu-exec.c b/cpu-exec.c >> index 5d9b518..0644383 100644 >> --- a/cpu-exec.c >> +++ b/cpu-exec.c >> @@ -364,8 +364,6 @@ static void cpu_handle_debug_exception(CPUArchStat= e *env) >> =20 >> /* main execution loop */ >> =20 >> -volatile sig_atomic_t exit_request; >> - >> int cpu_exec(CPUArchState *env) >> { >> CPUState *cpu =3D ENV_GET_CPU(env); >> @@ -394,20 +392,8 @@ int cpu_exec(CPUArchState *env) >> =20 >> current_cpu =3D cpu; >> =20 >> - /* As long as current_cpu is null, up to the assignment just abov= e, >> - * requests by other threads to exit the execution loop are expec= ted to >> - * be issued using the exit_request global. We must make sure tha= t our >> - * evaluation of the global value is performed past the current_c= pu >> - * value transition point, which requires a memory barrier as wel= l as >> - * an instruction scheduling constraint on modern architectures. = */ >> - smp_mb(); >> - >> rcu_read_lock(); >> =20 >> - if (unlikely(exit_request)) { >> - cpu->exit_request =3D 1; >> - } >> - >> cc->cpu_exec_enter(cpu); >> =20 >> /* Calculate difference between guest clock and host clock. >> @@ -496,7 +482,6 @@ int cpu_exec(CPUArchState *env) >> } >> } >> if (unlikely(cpu->exit_request)) { >> - cpu->exit_request =3D 0; >> cpu->exception_index =3D EXCP_INTERRUPT; >> cpu_loop_exit(cpu); >> } >> diff --git a/cpus.c b/cpus.c >> index 23c316c..2541c56 100644 >> --- a/cpus.c >> +++ b/cpus.c >> @@ -137,6 +137,8 @@ typedef struct TimersState { >> } TimersState; >> =20 >> static TimersState timers_state; >> +/* CPU associated to this thread. */ >> +static __thread CPUState *tcg_thread_cpu; >> =20 >> int64_t cpu_get_icount_raw(void) >> { >> @@ -661,12 +663,18 @@ static void cpu_handle_guest_debug(CPUState *cpu= ) >> cpu->stopped =3D true; >> } >> =20 >> +/** >> + * cpu_signal >> + * Signal handler when using TCG. >> + */ >> static void cpu_signal(int sig) >> { >> if (current_cpu) { >> cpu_exit(current_cpu); >> } >> - exit_request =3D 1; >> + >> + /* FIXME: We might want to check if the cpu is running? */ >> + tcg_thread_cpu->exit_request =3D true; > I guess the potential problem is race conditions here? What happens if > the cpu is signalled by two different threads for two different reasons= ? Hmmm yes, I need to take a look at that and check all the reason why it=20 should exit. But maybe it's OK, the first time the cpu get the signal it will set=20 exit_request.. and the second times as well? >> } >> =20 >> #ifdef CONFIG_LINUX >> @@ -1031,6 +1039,7 @@ static void *qemu_tcg_cpu_thread_fn(void *arg) >> { >> CPUState *cpu =3D arg; >> =20 >> + tcg_thread_cpu =3D cpu; >> qemu_tcg_init_cpu_signals(); >> qemu_thread_get_self(cpu->thread); >> =20 >> @@ -1393,7 +1402,8 @@ static void tcg_exec_all(void) >> if (next_cpu =3D=3D NULL) { >> next_cpu =3D first_cpu; >> } >> - for (; next_cpu !=3D NULL && !exit_request; next_cpu =3D CPU_NEXT= (next_cpu)) { >> + for (; next_cpu !=3D NULL && !first_cpu->exit_request; >> + next_cpu =3D CPU_NEXT(next_cpu)) { >> CPUState *cpu =3D next_cpu; >> CPUArchState *env =3D cpu->env_ptr; >> =20 >> @@ -1410,7 +1420,8 @@ static void tcg_exec_all(void) >> break; >> } >> } >> - exit_request =3D 0; >> + >> + first_cpu->exit_request =3D 0; >> } >> =20 >> void list_cpus(FILE *f, fprintf_function cpu_fprintf, const char *op= targ)