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From: "Alex Bennée" <alex.bennee@linaro.org>
To: Robert Foley <robert.foley@linaro.org>
Cc: peter.puhov@linaro.org, "Emilio G. Cota" <cota@braap.org>,
	richard.henderson@linaro.org, qemu-devel@nongnu.org
Subject: Re: [PATCH v8 03/74] cpu: introduce cpu_mutex_lock/unlock
Date: Mon, 11 May 2020 11:24:26 +0100
Message-ID: <873686hiqt.fsf@linaro.org> (raw)
In-Reply-To: <20200326193156.4322-4-robert.foley@linaro.org>


Robert Foley <robert.foley@linaro.org> writes:

> From: "Emilio G. Cota" <cota@braap.org>
>
> The few direct users of &cpu->lock will be converted soon.
>
> The per-thread bitmap introduced here might seem unnecessary,
> since a bool could just do. However, once we complete the
> conversion to per-vCPU locks, we will need to cover the use
> case where all vCPUs are locked by the same thread, which
> explains why the bitmap is introduced here.
>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
> Signed-off-by: Emilio G. Cota <cota@braap.org>
> Signed-off-by: Robert Foley <robert.foley@linaro.org>
> ---
>  cpus.c                | 48 +++++++++++++++++++++++++++++++++++++++++--
>  include/hw/core/cpu.h | 33 +++++++++++++++++++++++++++++
>  stubs/Makefile.objs   |  1 +
>  stubs/cpu-lock.c      | 28 +++++++++++++++++++++++++
>  4 files changed, 108 insertions(+), 2 deletions(-)
>  create mode 100644 stubs/cpu-lock.c
>
> diff --git a/cpus.c b/cpus.c
> index 71bd2f5d55..633734fb5c 100644
> --- a/cpus.c
> +++ b/cpus.c
> @@ -91,6 +91,47 @@ 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

I wonder if we should be asserting this somewhere? Given it's an init
time constant we can probably do it somewhere in the machine realise
stage. I think the value is set in  MachineState *ms->smp.max_cpus;

<snip>
> diff --git a/stubs/Makefile.objs b/stubs/Makefile.objs
> index 45be5dc0ed..d2dd6c94cc 100644
> --- a/stubs/Makefile.objs
> +++ b/stubs/Makefile.objs
> @@ -5,6 +5,7 @@ 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
> diff --git a/stubs/cpu-lock.c b/stubs/cpu-lock.c
> new file mode 100644
> index 0000000000..ca2ea8a9c2
> --- /dev/null
> +++ b/stubs/cpu-lock.c
> @@ -0,0 +1,28 @@
> +#include "qemu/osdep.h"
> +#include "hw/core/cpu.h"
> +
> +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);
> +    f(&cpu->lock, file, line);
> +#endif
> +}
> +
> +void cpu_mutex_unlock_impl(CPUState *cpu, const char *file, int line)
> +{
> +    qemu_mutex_unlock_impl(&cpu->lock, file, line);
> +}

I find this a little confusing because we clearly aren't stubbing
something out here - we are indeed doing a lock. What we seem to have is
effectively the linux-user implementation of cpu locking which currently
doesn't support qsp profiling.

> +bool cpu_mutex_locked(const CPUState *cpu)
> +{
> +    return true;
> +}
> +
> +bool no_cpu_mutex_locked(void)
> +{
> +    return true;
> +}

What functions care about these checks. I assume it's only system
emulation checks that are in common code. Maybe that indicates we could
achieve better separation of emulation and linux-user code. My worry is
by adding an assert in linux-user code we wouldn't actually be asserting
anything.

-- 
Alex Bennée


  reply index

Thread overview: 100+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-26 19:30 [PATCH v8 00/74] per-CPU locks Robert Foley
2020-03-26 19:30 ` [PATCH v8 01/74] cpu: convert queued work to a QSIMPLEQ Robert Foley
2020-03-26 19:30 ` [PATCH v8 02/74] cpu: rename cpu->work_mutex to cpu->lock Robert Foley
2020-05-11 14:48   ` Alex Bennée
2020-05-11 16:33     ` Robert Foley
2020-03-26 19:30 ` [PATCH v8 03/74] cpu: introduce cpu_mutex_lock/unlock Robert Foley
2020-05-11 10:24   ` Alex Bennée [this message]
2020-05-11 16:09     ` Robert Foley
2020-03-26 19:30 ` [PATCH v8 04/74] cpu: make qemu_work_cond per-cpu Robert Foley
2020-03-26 19:30 ` [PATCH v8 05/74] cpu: move run_on_cpu to cpus-common Robert Foley
2020-03-26 19:30 ` [PATCH v8 06/74] cpu: introduce process_queued_cpu_work_locked Robert Foley
2020-03-26 19:30 ` [PATCH v8 07/74] cpu: make per-CPU locks an alias of the BQL in TCG rr mode Robert Foley
2020-03-26 19:30 ` [PATCH v8 08/74] tcg-runtime: define helper_cpu_halted_set Robert Foley
2020-03-26 19:30 ` [PATCH v8 09/74] ppc: convert to helper_cpu_halted_set Robert Foley
2020-03-26 19:30 ` [PATCH v8 10/74] cris: " Robert Foley
2020-03-26 19:30 ` [PATCH v8 11/74] hppa: " Robert Foley
2020-03-26 19:30 ` [PATCH v8 12/74] m68k: " Robert Foley
2020-03-26 19:30 ` [PATCH v8 13/74] alpha: " Robert Foley
2020-03-26 19:30 ` [PATCH v8 14/74] microblaze: " Robert Foley
2020-03-26 19:30 ` [PATCH v8 15/74] cpu: define cpu_halted helpers Robert Foley
2020-03-26 19:30 ` [PATCH v8 16/74] tcg-runtime: convert to cpu_halted_set Robert Foley
2020-03-26 19:30 ` [PATCH v8 17/74] hw/semihosting: " Robert Foley
2020-05-11 10:25   ` Alex Bennée
2020-03-26 19:31 ` [PATCH v8 18/74] arm: convert to cpu_halted Robert Foley
2020-03-26 19:31 ` [PATCH v8 19/74] ppc: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 20/74] sh4: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 21/74] i386: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 22/74] lm32: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 23/74] m68k: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 24/74] mips: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 25/74] riscv: " Robert Foley
2020-05-11 10:40   ` Alex Bennée
2020-05-11 16:13     ` Robert Foley
2020-03-26 19:31 ` [PATCH v8 26/74] s390x: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 27/74] sparc: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 28/74] xtensa: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 29/74] gdbstub: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 30/74] openrisc: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 31/74] cpu-exec: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 32/74] cpu: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 33/74] cpu: define cpu_interrupt_request helpers Robert Foley
2020-03-26 19:31 ` [PATCH v8 34/74] ppc: use cpu_reset_interrupt Robert Foley
2020-03-26 19:31 ` [PATCH v8 35/74] exec: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 36/74] i386: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 37/74] s390x: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 38/74] openrisc: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 39/74] arm: convert to cpu_interrupt_request Robert Foley
2020-03-26 19:31 ` [PATCH v8 40/74] i386: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 41/74] i386/kvm: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 42/74] i386/hax-all: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 43/74] i386/whpx-all: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 44/74] i386/hvf: convert to cpu_request_interrupt Robert Foley
2020-03-26 19:31 ` [PATCH v8 45/74] ppc: convert to cpu_interrupt_request Robert Foley
2020-03-26 19:31 ` [PATCH v8 46/74] sh4: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 47/74] cris: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 48/74] hppa: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 49/74] lm32: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 50/74] m68k: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 51/74] mips: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 52/74] nios: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 53/74] s390x: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 54/74] alpha: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 55/74] moxie: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 56/74] sparc: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 57/74] openrisc: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 58/74] unicore32: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 59/74] microblaze: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 60/74] accel/tcg: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 61/74] cpu: convert to interrupt_request Robert Foley
2020-03-26 19:31 ` [PATCH v8 62/74] cpu: call .cpu_has_work with the CPU lock held Robert Foley
2020-03-26 19:31 ` [PATCH v8 63/74] cpu: introduce cpu_has_work_with_iothread_lock Robert Foley
2020-03-26 19:31 ` [PATCH v8 64/74] ppc: convert to cpu_has_work_with_iothread_lock Robert Foley
2020-03-26 19:31 ` [PATCH v8 65/74] mips: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 66/74] s390x: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 67/74] riscv: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 68/74] sparc: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 69/74] xtensa: " Robert Foley
2020-03-26 19:31 ` [PATCH v8 70/74] cpu: rename all_cpu_threads_idle to qemu_tcg_rr_all_cpu_threads_idle Robert Foley
2020-03-26 19:31 ` [PATCH v8 71/74] cpu: protect CPU state with cpu->lock instead of the BQL Robert Foley
2020-03-26 19:31 ` [PATCH v8 72/74] cpus-common: release BQL earlier in run_on_cpu Robert Foley
2020-03-26 19:31 ` [PATCH v8 73/74] cpu: add async_run_on_cpu_no_bql Robert Foley
2020-03-26 19:31 ` [PATCH v8 74/74] cputlb: queue async flush jobs without the BQL Robert Foley
2020-05-12 16:27   ` Alex Bennée
2020-05-12 19:26     ` Robert Foley
2020-05-18 13:46       ` Robert Foley
2020-05-20  4:46         ` Emilio G. Cota
2020-05-20 15:01           ` Robert Foley
2020-05-21 14:17             ` Robert Foley
2020-05-12 18:38   ` Alex Bennée
2020-03-26 22:58 ` [PATCH v8 00/74] per-CPU locks Aleksandar Markovic
2020-03-27  9:39   ` Alex Bennée
2020-03-27  9:50     ` Aleksandar Markovic
2020-03-27 10:24       ` Aleksandar Markovic
2020-03-27 17:21         ` Robert Foley
2020-03-27  5:14 ` Emilio G. Cota
2020-03-27 10:59   ` Philippe Mathieu-Daudé
2020-03-30  8:57     ` Stefan Hajnoczi
2020-03-27 18:23   ` Alex Bennée
2020-03-27 18:30   ` Robert Foley
2020-05-12 16:29 ` Alex Bennée

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