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[109.151.49.69]) by smtp.gmail.com with ESMTPSA id k187sm7824160wmb.13.2017.02.23.10.29.32 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 23 Feb 2017 10:29:36 -0800 (PST) Received: from zen.home (localhost [127.0.0.1]) by zen.linaro.local (Postfix) with ESMTP id EB43E3E06A0; Thu, 23 Feb 2017 18:29:27 +0000 (GMT) From: =?utf-8?q?Alex_Benn=C3=A9e?= To: rth@twiddle.net, peter.maydell@linaro.org Date: Thu, 23 Feb 2017 18:29:12 +0000 Message-Id: <20170223182927.7166-10-alex.bennee@linaro.org> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20170223182927.7166-1-alex.bennee@linaro.org> References: <20170223182927.7166-1-alex.bennee@linaro.org> MIME-Version: 1.0 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 2a00:1450:400c:c09::229 Subject: [Qemu-devel] [PATCH v14 09/24] tcg: remove global exit_request X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mttcg@listserver.greensocs.com, nikunj@linux.vnet.ibm.com, Peter Crosthwaite , jan.kiszka@siemens.com, mark.burton@greensocs.com, a.rigo@virtualopensystems.com, qemu-devel@nongnu.org, cota@braap.org, serge.fdrv@gmail.com, pbonzini@redhat.com, bobby.prani@gmail.com, =?utf-8?q?Alex_Benn=C3=A9e?= , bamvor.zhangjian@linaro.org, fred.konrad@greensocs.com Errors-To: qemu-devel-bounces+patch=linaro.org@nongnu.org Sender: "Qemu-devel" There are now only two uses of the global exit_request left. The first ensures we exit the run_loop when we first start to process pending work and in the kick handler. This is just as easily done by setting the first_cpu->exit_request flag. The second use is in the round robin kick routine. The global exit_request ensured every vCPU would set its local exit_request and cause a full exit of the loop. Now the iothread isn't being held while running we can just rely on the kick handler to push us out as intended. We lightly re-factor the main vCPU thread to ensure cpu->exit_requests cause us to exit the main loop and process any IO requests that might come along. As an cpu->exit_request may legitimately get squashed while processing the EXCP_INTERRUPT exception we also check cpu->queued_work_first to ensure queued work is expedited as soon as possible. Signed-off-by: Alex Bennée Reviewed-by: Richard Henderson --- v13 - also check cpu->queued_work_first in main loop. v5 - minor merge conflict with kick patch v4 - moved to after iothread unlocking patch - needed to remove kick exit_request as well. - remove extraneous cpu->exit_request check - remove stray exit_request setting - remove needless atomic operation --- cpu-exec-common.c | 2 -- cpu-exec.c | 20 +++++++------------- cpus.c | 19 +++++++++++-------- include/exec/exec-all.h | 3 --- 4 files changed, 18 insertions(+), 26 deletions(-) -- 2.11.0 diff --git a/cpu-exec-common.c b/cpu-exec-common.c index e2bc053372..0504a9457b 100644 --- a/cpu-exec-common.c +++ b/cpu-exec-common.c @@ -23,8 +23,6 @@ #include "exec/exec-all.h" #include "exec/memory-internal.h" -bool exit_request; - /* exit the current TB, but without causing any exception to be raised */ void cpu_loop_exit_noexc(CPUState *cpu) { diff --git a/cpu-exec.c b/cpu-exec.c index 1bd3d72002..85f14d4194 100644 --- a/cpu-exec.c +++ b/cpu-exec.c @@ -568,15 +568,13 @@ static inline void cpu_loop_exec_tb(CPUState *cpu, TranslationBlock *tb, *tb_exit = ret & TB_EXIT_MASK; switch (*tb_exit) { case TB_EXIT_REQUESTED: - /* Something asked us to stop executing - * chained TBs; just continue round the main - * loop. Whatever requested the exit will also - * have set something else (eg exit_request or - * interrupt_request) which we will handle - * next time around the loop. But we need to - * ensure the zeroing of tcg_exit_req (see cpu_tb_exec) - * comes before the next read of cpu->exit_request - * or cpu->interrupt_request. + /* Something asked us to stop executing chained TBs; just + * continue round the main loop. Whatever requested the exit + * will also have set something else (eg interrupt_request) + * which we will handle next time around the loop. But we + * need to ensure the tcg_exit_req read in generated code + * comes before the next read of cpu->exit_request or + * cpu->interrupt_request. */ smp_mb(); *last_tb = NULL; @@ -630,10 +628,6 @@ int cpu_exec(CPUState *cpu) rcu_read_lock(); - if (unlikely(atomic_mb_read(&exit_request))) { - cpu->exit_request = 1; - } - cc->cpu_exec_enter(cpu); /* Calculate difference between guest clock and host clock. diff --git a/cpus.c b/cpus.c index 0ae8f69be5..e165d18785 100644 --- a/cpus.c +++ b/cpus.c @@ -793,7 +793,6 @@ static inline int64_t qemu_tcg_next_kick(void) static void qemu_cpu_kick_rr_cpu(void) { CPUState *cpu; - atomic_mb_set(&exit_request, 1); do { cpu = atomic_mb_read(&tcg_current_rr_cpu); if (cpu) { @@ -1316,11 +1315,11 @@ static void *qemu_tcg_cpu_thread_fn(void *arg) start_tcg_kick_timer(); - /* process any pending work */ - atomic_mb_set(&exit_request, 1); - cpu = first_cpu; + /* process any pending work */ + cpu->exit_request = 1; + while (1) { /* Account partial waits to QEMU_CLOCK_VIRTUAL. */ qemu_account_warp_timer(); @@ -1329,7 +1328,8 @@ static void *qemu_tcg_cpu_thread_fn(void *arg) cpu = first_cpu; } - for (; cpu != NULL && !exit_request; cpu = CPU_NEXT(cpu)) { + while (cpu && !cpu->queued_work_first && !cpu->exit_request) { + atomic_mb_set(&tcg_current_rr_cpu, cpu); qemu_clock_enable(QEMU_CLOCK_VIRTUAL, @@ -1349,12 +1349,15 @@ static void *qemu_tcg_cpu_thread_fn(void *arg) break; } - } /* for cpu.. */ + cpu = CPU_NEXT(cpu); + } /* while (cpu && !cpu->exit_request).. */ + /* Does not need atomic_mb_set because a spurious wakeup is okay. */ atomic_set(&tcg_current_rr_cpu, NULL); - /* Pairs with smp_wmb in qemu_cpu_kick. */ - atomic_mb_set(&exit_request, 0); + if (cpu && cpu->exit_request) { + atomic_mb_set(&cpu->exit_request, 0); + } handle_icount_deadline(); diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h index 4e34fc4cc1..82f0e12327 100644 --- a/include/exec/exec-all.h +++ b/include/exec/exec-all.h @@ -404,7 +404,4 @@ bool memory_region_is_unassigned(MemoryRegion *mr); /* vl.c */ extern int singlestep; -/* cpu-exec.c, accessed with atomic_mb_read/atomic_mb_set */ -extern bool exit_request; - #endif