Re: [Qemu-devel] [PATCH 06/12] cpus-common: move CPU list management to common code

["Alex Bennée" <alex.bennee@linaro.org>]

Paolo Bonzini <pbonzini@redhat.com> writes:

> Add a mutex for the CPU list to system emulation, as it will be used to
> manage safe work.  Abstract manipulation of the CPU list in new functions
> cpu_list_add and cpu_list_remove.
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
<snip>
> index a440bcb..73d0c2f 100644

What tree are you based off? git-am is having trouble applying this
patch and the -3way fall back gets very confused:

    Applying: cpus-common: move CPU list management to common code
    fatal: sha1 information is lacking or useless (exec.c).
    error: could not build fake ancestor
    Patch failed at 0001 cpus-common: move CPU list management to common code
    The copy of the patch that failed is found in: .git/rebase-apply/patch
    When you have resolved this problem, run "git am --continue".
    If you prefer to skip this patch, run "git am --skip" instead.
    To restore the original branch and stop patching, run "git am --abort".

I think this is because it looks to find real SHA1's to replay the diff.
Your root commit (0308431) doesn't seem to exist in any public tree.

> --- a/Makefile.target
> +++ b/Makefile.target
> @@ -86,7 +86,7 @@ all: $(PROGS) stap
>  # cpu emulator library
>  obj-y = exec.o translate-all.o cpu-exec.o
>  obj-y += translate-common.o
> -obj-y += cpu-exec-common.o
> +obj-y += cpu-exec-common.o cpus-common.o
>  obj-y += tcg/tcg.o tcg/tcg-op.o tcg/optimize.o
>  obj-$(CONFIG_TCG_INTERPRETER) += tci.o
>  obj-y += tcg/tcg-common.o
> diff --git a/bsd-user/main.c b/bsd-user/main.c
> index b4a0a00..461641a 100644
> --- a/bsd-user/main.c
> +++ b/bsd-user/main.c
> @@ -94,14 +94,6 @@ void fork_end(int child)
>      }
>  }
>
> -void cpu_list_lock(void)
> -{
> -}
> -
> -void cpu_list_unlock(void)
> -{
> -}
> -
>  #ifdef TARGET_I386
>  /***********************************************************/
>  /* CPUX86 core interface */
> @@ -747,6 +739,7 @@ int main(int argc, char **argv)
>      if (argc <= 1)
>          usage();
>
> +    qemu_init_cpu_list();
>      module_call_init(MODULE_INIT_QOM);
>
>      if ((envlist = envlist_create()) == NULL) {
> diff --git a/cpus-common.c b/cpus-common.c
> new file mode 100644
> index 0000000..642e923
> --- /dev/null
> +++ b/cpus-common.c
> @@ -0,0 +1,74 @@
> +/*
> + * CPU thread main loop - common bits for user and system mode emulation
> + *
> + *  Copyright (c) 2003-2005 Fabrice Bellard
> + *
> + * This library is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2 of the License, or (at your option) any later version.
> + *
> + * This library is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with this library; if not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#include "qemu/osdep.h"
> +#include "cpu.h"
> +#include "sysemu/cpus.h"
> +#include "exec/memory-internal.h"
> +
> +static QemuMutex qemu_cpu_list_mutex;
> +
> +void qemu_init_cpu_list(void)
> +{
> +    qemu_mutex_init(&qemu_cpu_list_mutex);
> +}
> +
> +void cpu_list_lock(void)
> +{
> +    qemu_mutex_lock(&qemu_cpu_list_mutex);
> +}
> +
> +void cpu_list_unlock(void)
> +{
> +    qemu_mutex_unlock(&qemu_cpu_list_mutex);
> +}
> +
> +static int cpu_get_free_index(void)
> +{
> +    CPUState *some_cpu;
> +    int cpu_index = 0;
> +
> +    CPU_FOREACH(some_cpu) {
> +        cpu_index++;
> +    }
> +    return cpu_index;
> +}
> +
> +void cpu_list_add(CPUState *cpu)
> +{
> +    qemu_mutex_lock(&qemu_cpu_list_mutex);
> +    if (cpu->cpu_index == UNASSIGNED_CPU_INDEX) {
> +        cpu->cpu_index = cpu_get_free_index();
> +        assert(cpu->cpu_index != UNASSIGNED_CPU_INDEX);
> +    }
> +
> +    QTAILQ_INSERT_TAIL(&cpus, cpu, node);
> +    qemu_mutex_unlock(&qemu_cpu_list_mutex);
> +}
> +
> +void cpu_list_remove(CPUState *cpu)
> +{
> +    /* ??? How is this serialized against CPU_FOREACH? */
> +    qemu_mutex_lock(&qemu_cpu_list_mutex);
> +    if (QTAILQ_IN_USE(cpu, node)) {
> +        QTAILQ_REMOVE(&cpus, cpu, node);
> +    }
> +    cpu->cpu_index = UNASSIGNED_CPU_INDEX;
> +    qemu_mutex_unlock(&qemu_cpu_list_mutex);
> +}
> diff --git a/exec.c b/exec.c
> index 286f5cd..784990c 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -598,31 +598,11 @@ AddressSpace *cpu_get_address_space(CPUState *cpu, int asidx)
>  }
>  #endif
>
> -static int cpu_get_free_index(void)
> -{
> -    CPUState *some_cpu;
> -    int cpu_index = 0;
> -
> -    CPU_FOREACH(some_cpu) {
> -        cpu_index++;
> -    }
> -    return cpu_index;
> -}
> -
>  void cpu_exec_exit(CPUState *cpu)
>  {
>      CPUClass *cc = CPU_GET_CLASS(cpu);
>
> -    cpu_list_lock();
> -    if (!QTAILQ_IN_USE(cpu, node)) {
> -        /* there is nothing to undo since cpu_exec_init() hasn't been called */
> -        cpu_list_unlock();
> -        return;
> -    }
> -
> -    QTAILQ_REMOVE(&cpus, cpu, node);
> -    cpu->cpu_index = UNASSIGNED_CPU_INDEX;
> -    cpu_list_unlock();
> +    cpu_list_remove(cpu);
>
>      if (cc->vmsd != NULL) {
>          vmstate_unregister(NULL, cc->vmsd, cpu);
> @@ -658,13 +638,7 @@ void cpu_exec_init(CPUState *cpu, Error **errp)
>      object_ref(OBJECT(cpu->memory));
>  #endif
>
> -    cpu_list_lock();
> -    if (cpu->cpu_index == UNASSIGNED_CPU_INDEX) {
> -        cpu->cpu_index = cpu_get_free_index();
> -        assert(cpu->cpu_index != UNASSIGNED_CPU_INDEX);
> -    }
> -    QTAILQ_INSERT_TAIL(&cpus, cpu, node);
> -    cpu_list_unlock();
> +    cpu_list_add(cpu);
>
>  #ifndef CONFIG_USER_ONLY
>      if (qdev_get_vmsd(DEVICE(cpu)) == NULL) {
> diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h
> index b6a7059..c694d16 100644
> --- a/include/exec/cpu-all.h
> +++ b/include/exec/cpu-all.h
> @@ -187,6 +187,10 @@ void address_space_stq(AddressSpace *as, hwaddr addr, uint64_t val,
>                              MemTxAttrs attrs, MemTxResult *result);
>  #endif
>
> +/* The CPU list lock nests outside tb_lock/tb_unlock.  */
> +void cpu_list_lock(void);
> +void cpu_list_unlock(void);
> +
>  /* page related stuff */
>
>  #define TARGET_PAGE_SIZE (1 << TARGET_PAGE_BITS)
> diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h
> index 952bcfe..1d41452 100644
> --- a/include/exec/cpu-common.h
> +++ b/include/exec/cpu-common.h
> @@ -23,6 +23,8 @@ typedef struct CPUListState {
>      FILE *file;
>  } CPUListState;
>
> +void qemu_init_cpu_list(void);
> +
>  #if !defined(CONFIG_USER_ONLY)
>
>  enum device_endian {
> diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
> index a0e87be..36ab8b6 100644
> --- a/include/exec/exec-all.h
> +++ b/include/exec/exec-all.h
> @@ -56,17 +56,6 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
>                                target_ulong pc, target_ulong cs_base,
>                                uint32_t flags,
>                                int cflags);
> -#if defined(CONFIG_USER_ONLY)
> -void cpu_list_lock(void);
> -void cpu_list_unlock(void);
> -#else
> -static inline void cpu_list_unlock(void)
> -{
> -}
> -static inline void cpu_list_lock(void)
> -{
> -}
> -#endif
>
>  void cpu_exec_init(CPUState *cpu, Error **errp);
>  void QEMU_NORETURN cpu_loop_exit(CPUState *cpu);
> diff --git a/include/qom/cpu.h b/include/qom/cpu.h
> index 4aa9e61..ea3233f 100644
> --- a/include/qom/cpu.h
> +++ b/include/qom/cpu.h
> @@ -545,6 +545,18 @@ static inline int cpu_asidx_from_attrs(CPUState *cpu, MemTxAttrs attrs)
>  #endif
>
>  /**
> + * cpu_list_add:
> + * @cpu: The CPU to be added to the list of CPUs.
> + */
> +void cpu_list_add(CPUState *cpu);
> +
> +/**
> + * cpu_list_remove:
> + * @cpu: The CPU to be removed from the list of CPUs.
> + */
> +void cpu_list_remove(CPUState *cpu);
> +
> +/**
>   * cpu_reset:
>   * @cpu: The CPU whose state is to be reset.
>   */
> diff --git a/linux-user/main.c b/linux-user/main.c
> index 6195c68..bd5b58f 100644
> --- a/linux-user/main.c
> +++ b/linux-user/main.c
> @@ -111,7 +111,6 @@ int cpu_get_pic_interrupt(CPUX86State *env)
>     We don't require a full sync, only that no cpus are executing guest code.
>     The alternative is to map target atomic ops onto host equivalents,
>     which requires quite a lot of per host/target work.  */
> -static QemuMutex cpu_list_mutex;
>  static QemuMutex exclusive_lock;
>  static QemuCond exclusive_cond;
>  static QemuCond exclusive_resume;
> @@ -119,7 +118,6 @@ static int pending_cpus;
>
>  void qemu_init_cpu_loop(void)
>  {
> -    qemu_mutex_init(&cpu_list_mutex);
>      qemu_mutex_init(&exclusive_lock);
>      qemu_cond_init(&exclusive_cond);
>      qemu_cond_init(&exclusive_resume);
> @@ -128,6 +126,7 @@ void qemu_init_cpu_loop(void)
>  /* Make sure everything is in a consistent state for calling fork().  */
>  void fork_start(void)
>  {
> +    cpu_list_lock();
>      qemu_mutex_lock(&tcg_ctx.tb_ctx.tb_lock);
>      qemu_mutex_lock(&exclusive_lock);
>      mmap_fork_start();
> @@ -147,14 +146,15 @@ void fork_end(int child)
>          }
>          pending_cpus = 0;
>          qemu_mutex_init(&exclusive_lock);
> -        qemu_mutex_init(&cpu_list_mutex);
>          qemu_cond_init(&exclusive_cond);
>          qemu_cond_init(&exclusive_resume);
>          qemu_mutex_init(&tcg_ctx.tb_ctx.tb_lock);
> +        qemu_init_cpu_list();
>          gdbserver_fork(thread_cpu);
>      } else {
>          qemu_mutex_unlock(&exclusive_lock);
>          qemu_mutex_unlock(&tcg_ctx.tb_ctx.tb_lock);
> +        cpu_list_unlock();
>      }
>  }
>
> @@ -221,16 +221,6 @@ static inline void cpu_exec_end(CPUState *cpu)
>      qemu_mutex_unlock(&exclusive_lock);
>  }
>
> -void cpu_list_lock(void)
> -{
> -    qemu_mutex_lock(&cpu_list_mutex);
> -}
> -
> -void cpu_list_unlock(void)
> -{
> -    qemu_mutex_unlock(&cpu_list_mutex);
> -}
> -
>
>  #ifdef TARGET_I386
>  /***********************************************************/
> @@ -4240,6 +4230,7 @@ int main(int argc, char **argv, char **envp)
>      int ret;
>      int execfd;
>
> +    qemu_init_cpu_list();
>      qemu_init_cpu_loop();
>      module_call_init(MODULE_INIT_QOM);
>
> diff --git a/vl.c b/vl.c
> index b3c80d5..1445935 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -2965,6 +2965,7 @@ int main(int argc, char **argv, char **envp)
>      Error *err = NULL;
>      bool list_data_dirs = false;
>
> +    qemu_init_cpu_list();
>      qemu_init_cpu_loop();
>      qemu_mutex_lock_iothread();


--
Alex Bennée