Re: [PATCH 02/19] cpu: convert queued work to a QSIMPLEQ

[Robert Foley]

On Sun, 24 May 2020 at 06:21, Philippe Mathieu-Daudé <address@hidden> wrote:
>
> On 5/22/20 6:07 PM, Robert Foley wrote:
> > From: "Emilio G. Cota" <address@hidden>
> >
> > Instead of open-coding it.
>
> Please use a full sentence (repeating the patch subject):
>
> "Convert queued work to a QSIMPLEQ instead of open-coding it."
>
> (Not all email clients display the subject preceding the content).

OK, I will update this commit message.

Thanks & Regards,
-Rob
>
> Otherwise:
> Reviewed-by: Philippe Mathieu-Daudé <address@hidden>
>
> >
> > While at it, make sure that all accesses to the list are
> > performed while holding the list's lock.
> >
> > Reviewed-by: Richard Henderson <address@hidden>
> > Reviewed-by: Alex Bennée <address@hidden>
> > Signed-off-by: Emilio G. Cota <address@hidden>
> > Signed-off-by: Robert Foley <address@hidden>
> > ---
> >  cpus-common.c         | 25 ++++++++-----------------
> >  cpus.c                | 14 ++++++++++++--
> >  hw/core/cpu.c         |  1 +
> >  include/hw/core/cpu.h |  6 +++---
> >  4 files changed, 24 insertions(+), 22 deletions(-)
> >
> > diff --git a/cpus-common.c b/cpus-common.c
> > index 55d5df8923..210fc7fc39 100644
> > --- a/cpus-common.c
> > +++ b/cpus-common.c
> > @@ -97,7 +97,7 @@ void cpu_list_remove(CPUState *cpu)
> >  }
> >
> >  struct qemu_work_item {
> > -    struct qemu_work_item *next;
> > +    QSIMPLEQ_ENTRY(qemu_work_item) node;
> >      run_on_cpu_func func;
> >      run_on_cpu_data data;
> >      bool free, exclusive, done;
> > @@ -106,13 +106,7 @@ struct qemu_work_item {
> >  static void queue_work_on_cpu(CPUState *cpu, struct qemu_work_item *wi)
> >  {
> >      qemu_mutex_lock(&cpu->work_mutex);
> > -    if (cpu->queued_work_first == NULL) {
> > -        cpu->queued_work_first = wi;
> > -    } else {
> > -        cpu->queued_work_last->next = wi;
> > -    }
> > -    cpu->queued_work_last = wi;
> > -    wi->next = NULL;
> > +    QSIMPLEQ_INSERT_TAIL(&cpu->work_list, wi, node);
> >      wi->done = false;
> >      qemu_mutex_unlock(&cpu->work_mutex);
> >
> > @@ -306,17 +300,14 @@ void process_queued_cpu_work(CPUState *cpu)
> >  {
> >      struct qemu_work_item *wi;
> >
> > -    if (cpu->queued_work_first == NULL) {
> > +    qemu_mutex_lock(&cpu->work_mutex);
> > +    if (QSIMPLEQ_EMPTY(&cpu->work_list)) {
> > +        qemu_mutex_unlock(&cpu->work_mutex);
> >          return;
> >      }
> > -
> > -    qemu_mutex_lock(&cpu->work_mutex);
> > -    while (cpu->queued_work_first != NULL) {
> > -        wi = cpu->queued_work_first;
> > -        cpu->queued_work_first = wi->next;
> > -        if (!cpu->queued_work_first) {
> > -            cpu->queued_work_last = NULL;
> > -        }
> > +    while (!QSIMPLEQ_EMPTY(&cpu->work_list)) {
> > +        wi = QSIMPLEQ_FIRST(&cpu->work_list);
> > +        QSIMPLEQ_REMOVE_HEAD(&cpu->work_list, node);
> >          qemu_mutex_unlock(&cpu->work_mutex);
> >          if (wi->exclusive) {
> >              /* Running work items outside the BQL avoids the following 
> > deadlock:
> > diff --git a/cpus.c b/cpus.c
> > index 5670c96bcf..af44027549 100644
> > --- a/cpus.c
> > +++ b/cpus.c
> > @@ -97,9 +97,19 @@ bool cpu_is_stopped(CPUState *cpu)
> >      return cpu->stopped || !runstate_is_running();
> >  }
> >
> > +static inline bool cpu_work_list_empty(CPUState *cpu)
> > +{
> > +    bool ret;
> > +
> > +    qemu_mutex_lock(&cpu->work_mutex);
> > +    ret = QSIMPLEQ_EMPTY(&cpu->work_list);
> > +    qemu_mutex_unlock(&cpu->work_mutex);
> > +    return ret;
> > +}
> > +
> >  static bool cpu_thread_is_idle(CPUState *cpu)
> >  {
> > -    if (cpu->stop || cpu->queued_work_first) {
> > +    if (cpu->stop || !cpu_work_list_empty(cpu)) {
> >          return false;
> >      }
> >      if (cpu_is_stopped(cpu)) {
> > @@ -1498,7 +1508,7 @@ static void *qemu_tcg_rr_cpu_thread_fn(void *arg)
> >              cpu = first_cpu;
> >          }
> >
> > -        while (cpu && !cpu->queued_work_first && !cpu->exit_request) {
> > +        while (cpu && cpu_work_list_empty(cpu) && !cpu->exit_request) {
> >
> >              atomic_mb_set(&tcg_current_rr_cpu, cpu);
> >              current_cpu = cpu;
> > diff --git a/hw/core/cpu.c b/hw/core/cpu.c
> > index 5284d384fb..77703d62b7 100644
> > --- a/hw/core/cpu.c
> > +++ b/hw/core/cpu.c
> > @@ -368,6 +368,7 @@ static void cpu_common_initfn(Object *obj)
> >      cpu->nr_threads = 1;
> >
> >      qemu_mutex_init(&cpu->work_mutex);
> > +    QSIMPLEQ_INIT(&cpu->work_list);
> >      QTAILQ_INIT(&cpu->breakpoints);
> >      QTAILQ_INIT(&cpu->watchpoints);
> >
> > diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h
> > index 07f7698155..d78ff1d165 100644
> > --- a/include/hw/core/cpu.h
> > +++ b/include/hw/core/cpu.h
> > @@ -331,8 +331,8 @@ struct qemu_work_item;
> >   * @opaque: User data.
> >   * @mem_io_pc: Host Program Counter at which the memory was accessed.
> >   * @kvm_fd: vCPU file descriptor for KVM.
> > - * @work_mutex: Lock to prevent multiple access to queued_work_*.
> > - * @queued_work_first: First asynchronous work pending.
> > + * @work_mutex: Lock to prevent multiple access to @work_list.
> > + * @work_list: List of pending asynchronous work.
> >   * @trace_dstate_delayed: Delayed changes to trace_dstate (includes all 
> > changes
> >   *                        to @trace_dstate).
> >   * @trace_dstate: Dynamic tracing state of events for this vCPU (bitmask).
> > @@ -376,7 +376,7 @@ struct CPUState {
> >      sigjmp_buf jmp_env;
> >
> >      QemuMutex work_mutex;
> > -    struct qemu_work_item *queued_work_first, *queued_work_last;
> > +    QSIMPLEQ_HEAD(, qemu_work_item) work_list;
> >
> >      CPUAddressSpace *cpu_ases;
> >      int num_ases;
> >
>