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That's all we know. X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: robert.foley@linaro.org, cota@braap.org, peter.puhov@linaro.org, alex.bennee@linaro.org, Eduardo Habkost Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) From: "Emilio G. Cota" Add a comment about how atomic_read works here. The comment refers to a "BQL-less CPU loop", which will materialize toward the end of this series. Note that the modifications to cpu_reset_interrupt are there to avoid deadlock during the CPU lock transition; once that is complete, cpu_interrupt_request will be simple again. Reviewed-by: Richard Henderson Reviewed-by: Alex Benn=C3=A9e Signed-off-by: Emilio G. Cota Signed-off-by: Robert Foley --- hw/core/cpu.c | 27 +++++++++++++++++++++------ include/hw/core/cpu.h | 37 +++++++++++++++++++++++++++++++++++++ 2 files changed, 58 insertions(+), 6 deletions(-) diff --git a/hw/core/cpu.c b/hw/core/cpu.c index 64a1bf3e92..d3223f6d42 100644 --- a/hw/core/cpu.c +++ b/hw/core/cpu.c @@ -99,14 +99,29 @@ static void cpu_common_get_memory_mapping(CPUState *cpu, * BQL here if we need to. cpu_interrupt assumes it is held.*/ void cpu_reset_interrupt(CPUState *cpu, int mask) { - bool need_lock =3D !qemu_mutex_iothread_locked(); + bool has_bql =3D qemu_mutex_iothread_locked(); + bool has_cpu_lock =3D cpu_mutex_locked(cpu); =20 - if (need_lock) { - qemu_mutex_lock_iothread(); + if (has_bql) { + if (has_cpu_lock) { + atomic_set(&cpu->interrupt_request, cpu->interrupt_request & ~= mask); + } else { + cpu_mutex_lock(cpu); + atomic_set(&cpu->interrupt_request, cpu->interrupt_request & ~= mask); + cpu_mutex_unlock(cpu); + } + return; + } + + if (has_cpu_lock) { + cpu_mutex_unlock(cpu); } - cpu->interrupt_request &=3D ~mask; - if (need_lock) { - qemu_mutex_unlock_iothread(); + qemu_mutex_lock_iothread(); + cpu_mutex_lock(cpu); + atomic_set(&cpu->interrupt_request, cpu->interrupt_request & ~mask); + qemu_mutex_unlock_iothread(); + if (!has_cpu_lock) { + cpu_mutex_unlock(cpu); } } =20 diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h index 92069ebc59..6f2c005171 100644 --- a/include/hw/core/cpu.h +++ b/include/hw/core/cpu.h @@ -522,6 +522,43 @@ static inline void cpu_halted_set(CPUState *cpu, uint3= 2_t val) cpu_mutex_unlock(cpu); } =20 +/* + * When sending an interrupt, setters OR the appropriate bit and kick the + * destination vCPU. The latter can then read interrupt_request without + * acquiring the CPU lock, because once the kick-induced completes, they'l= l read + * an up-to-date interrupt_request. + * Setters always acquire the lock, which guarantees that (1) concurrent + * updates from different threads won't result in data races, and (2) the + * BQL-less CPU loop will always see an up-to-date interrupt_request, sinc= e the + * loop holds the CPU lock. + */ +static inline uint32_t cpu_interrupt_request(CPUState *cpu) +{ + return atomic_read(&cpu->interrupt_request); +} + +static inline void cpu_interrupt_request_or(CPUState *cpu, uint32_t mask) +{ + if (cpu_mutex_locked(cpu)) { + atomic_set(&cpu->interrupt_request, cpu->interrupt_request | mask); + return; + } + cpu_mutex_lock(cpu); + atomic_set(&cpu->interrupt_request, cpu->interrupt_request | mask); + cpu_mutex_unlock(cpu); +} + +static inline void cpu_interrupt_request_set(CPUState *cpu, uint32_t val) +{ + if (cpu_mutex_locked(cpu)) { + atomic_set(&cpu->interrupt_request, val); + return; + } + cpu_mutex_lock(cpu); + atomic_set(&cpu->interrupt_request, val); + cpu_mutex_unlock(cpu); +} + static inline void cpu_tb_jmp_cache_clear(CPUState *cpu) { unsigned int i; --=20 2.17.1