From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58549) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gDJFO-0004U5-Sx for qemu-devel@nongnu.org; Thu, 18 Oct 2018 21:06:42 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gDJFL-0002js-Bq for qemu-devel@nongnu.org; Thu, 18 Oct 2018 21:06:38 -0400 Received: from out5-smtp.messagingengine.com ([66.111.4.29]:53827) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gDJFJ-0002aF-D4 for qemu-devel@nongnu.org; Thu, 18 Oct 2018 21:06:35 -0400 From: "Emilio G. Cota" Date: Thu, 18 Oct 2018 21:05:32 -0400 Message-Id: <20181019010625.25294-4-cota@braap.org> In-Reply-To: <20181019010625.25294-1-cota@braap.org> References: <20181019010625.25294-1-cota@braap.org> Subject: [Qemu-devel] [RFC v3 03/56] cpu: introduce cpu_mutex_lock/unlock List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Paolo Bonzini , Peter Crosthwaite , Richard Henderson The few direct users of &cpu->lock will be converted soon. Cc: Peter Crosthwaite Cc: Richard Henderson Signed-off-by: Emilio G. Cota --- include/qom/cpu.h | 26 ++++++++++++++++++++++++ cpus.c | 48 +++++++++++++++++++++++++++++++++++++++++++-- stubs/cpu-lock.c | 15 ++++++++++++++ stubs/Makefile.objs | 1 + 4 files changed, 88 insertions(+), 2 deletions(-) create mode 100644 stubs/cpu-lock.c diff --git a/include/qom/cpu.h b/include/qom/cpu.h index b813ca28fa..1292e7aa33 100644 --- a/include/qom/cpu.h +++ b/include/qom/cpu.h @@ -452,6 +452,32 @@ extern struct CPUTailQ cpus; extern __thread CPUState *current_cpu; +/** + * cpu_mutex_lock - lock a CPU's mutex + * @cpu: the CPU whose mutex is to be locked + * + * To avoid deadlock, a CPU's mutex must be acquired after the BQL. + */ +#define cpu_mutex_lock(cpu) \ + cpu_mutex_lock_impl(cpu, __FILE__, __LINE__) +void cpu_mutex_lock_impl(CPUState *cpu, const char *file, int line); + +/** + * cpu_mutex_unlock - unlock a CPU's mutex + * @cpu: the CPU whose mutex is to be unlocked + */ +#define cpu_mutex_unlock(cpu) \ + cpu_mutex_unlock_impl(cpu, __FILE__, __LINE__) +void cpu_mutex_unlock_impl(CPUState *cpu, const char *file, int line); + +/** + * cpu_mutex_locked - check whether a CPU's mutex is locked + * @cpu: the CPU of interest + * + * Returns true if the calling thread is currently holding the CPU's mutex. + */ +bool cpu_mutex_locked(const CPUState *cpu); + static inline void cpu_tb_jmp_cache_clear(CPUState *cpu) { unsigned int i; diff --git a/cpus.c b/cpus.c index b2a9698dc0..a190651653 100644 --- a/cpus.c +++ b/cpus.c @@ -83,6 +83,47 @@ static unsigned int throttle_percentage; #define CPU_THROTTLE_PCT_MAX 99 #define CPU_THROTTLE_TIMESLICE_NS 10000000 +/* XXX: is this really the max number of CPUs? */ +#define CPU_LOCK_BITMAP_SIZE 2048 + +/* + * Note: we index the bitmap with cpu->cpu_index + 1 so that the logic + * also works during early CPU initialization, when cpu->cpu_index is set to + * UNASSIGNED_CPU_INDEX == -1. + */ +static __thread DECLARE_BITMAP(cpu_lock_bitmap, CPU_LOCK_BITMAP_SIZE); + +static bool no_cpu_mutex_locked(void) +{ + return bitmap_empty(cpu_lock_bitmap, CPU_LOCK_BITMAP_SIZE); +} + +void cpu_mutex_lock_impl(CPUState *cpu, const char *file, int line) +{ +/* coverity gets confused by the indirect function call */ +#ifdef __COVERITY__ + qemu_mutex_lock_impl(&cpu->lock, file, line); +#else + QemuMutexLockFunc f = atomic_read(&qemu_mutex_lock_func); + + g_assert(!cpu_mutex_locked(cpu)); + set_bit(cpu->cpu_index + 1, cpu_lock_bitmap); + f(&cpu->lock, file, line); +#endif +} + +void cpu_mutex_unlock_impl(CPUState *cpu, const char *file, int line) +{ + g_assert(cpu_mutex_locked(cpu)); + qemu_mutex_unlock_impl(&cpu->lock, file, line); + clear_bit(cpu->cpu_index + 1, cpu_lock_bitmap); +} + +bool cpu_mutex_locked(const CPUState *cpu) +{ + return test_bit(cpu->cpu_index + 1, cpu_lock_bitmap); +} + bool cpu_is_stopped(CPUState *cpu) { return cpu->stopped || !runstate_is_running(); @@ -92,9 +133,9 @@ static inline bool cpu_work_list_empty(CPUState *cpu) { bool ret; - qemu_mutex_lock(&cpu->lock); + cpu_mutex_lock(cpu); ret = QSIMPLEQ_EMPTY(&cpu->work_list); - qemu_mutex_unlock(&cpu->lock); + cpu_mutex_unlock(cpu); return ret; } @@ -1843,6 +1884,9 @@ void qemu_mutex_lock_iothread_impl(const char *file, int line) { QemuMutexLockFunc bql_lock = atomic_read(&qemu_bql_mutex_lock_func); + /* prevent deadlock with CPU mutex */ + g_assert(no_cpu_mutex_locked()); + g_assert(!qemu_mutex_iothread_locked()); bql_lock(&qemu_global_mutex, file, line); iothread_locked = true; diff --git a/stubs/cpu-lock.c b/stubs/cpu-lock.c new file mode 100644 index 0000000000..bc54f00b78 --- /dev/null +++ b/stubs/cpu-lock.c @@ -0,0 +1,15 @@ +#include "qemu/osdep.h" +#include "qom/cpu.h" + +void cpu_mutex_lock_impl(CPUState *cpu, const char *file, int line) +{ +} + +void cpu_mutex_unlock_impl(CPUState *cpu, const char *file, int line) +{ +} + +bool cpu_mutex_locked(const CPUState *cpu) +{ + return true; +} diff --git a/stubs/Makefile.objs b/stubs/Makefile.objs index 53d3f32cb2..fbcdc0256d 100644 --- a/stubs/Makefile.objs +++ b/stubs/Makefile.objs @@ -8,6 +8,7 @@ stub-obj-y += blockdev-close-all-bdrv-states.o stub-obj-y += clock-warp.o stub-obj-y += cpu-get-clock.o stub-obj-y += cpu-get-icount.o +stub-obj-y += cpu-lock.o stub-obj-y += dump.o stub-obj-y += error-printf.o stub-obj-y += fdset.o -- 2.17.1