Patchwork [7/8] timers: document (future) locking rules for icount

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Submitter Paolo Bonzini
Date Oct. 8, 2013, 8:47 a.m.
Message ID <1381222058-16701-8-git-send-email-pbonzini@redhat.com>
Download mbox | patch
Permalink /patch/281368/
State New
Headers show

Comments

Paolo Bonzini - Oct. 8, 2013, 8:47 a.m.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 cpus.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)
Alex Bligh - Oct. 8, 2013, 4:56 p.m.
On 8 Oct 2013, at 09:47, Paolo Bonzini wrote:

> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Reviewed-by: Alex Bligh <alex@alex.org.uk>

> ---
> cpus.c | 15 +++++++++++----
> 1 file changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/cpus.c b/cpus.c
> index 01acce2..bc675a4 100644
> --- a/cpus.c
> +++ b/cpus.c
> @@ -98,17 +98,22 @@ static bool all_cpu_threads_idle(void)
> /***********************************************************/
> /* guest cycle counter */
> 
> +/* Protected by TimersState seqlock */
> +
> +/* Compensate for varying guest execution speed.  */
> +static int64_t qemu_icount_bias;
> +static int64_t vm_clock_warp_start;
> /* Conversion factor from emulated instructions to virtual clock ticks.  */
> static int icount_time_shift;
> /* Arbitrarily pick 1MIPS as the minimum allowable speed.  */
> #define MAX_ICOUNT_SHIFT 10
> -/* Compensate for varying guest execution speed.  */
> -static int64_t qemu_icount_bias;
> +
> +/* Only written by TCG thread */
> +static int64_t qemu_icount;
> +
> static QEMUTimer *icount_rt_timer;
> static QEMUTimer *icount_vm_timer;
> static QEMUTimer *icount_warp_timer;
> -static int64_t vm_clock_warp_start;
> -static int64_t qemu_icount;
> 
> typedef struct TimersState {
>     int64_t cpu_ticks_prev;
> @@ -232,6 +237,8 @@ static void icount_adjust(void)
>     int64_t cur_time;
>     int64_t cur_icount;
>     int64_t delta;
> +
> +    /* Protected by TimersState mutex.  */
>     static int64_t last_delta;
> 
>     /* If the VM is not running, then do nothing.  */
> -- 
> 1.8.3.1
> 
> 
> 
>

Patch

diff --git a/cpus.c b/cpus.c
index 01acce2..bc675a4 100644
--- a/cpus.c
+++ b/cpus.c
@@ -98,17 +98,22 @@  static bool all_cpu_threads_idle(void)
 /***********************************************************/
 /* guest cycle counter */
 
+/* Protected by TimersState seqlock */
+
+/* Compensate for varying guest execution speed.  */
+static int64_t qemu_icount_bias;
+static int64_t vm_clock_warp_start;
 /* Conversion factor from emulated instructions to virtual clock ticks.  */
 static int icount_time_shift;
 /* Arbitrarily pick 1MIPS as the minimum allowable speed.  */
 #define MAX_ICOUNT_SHIFT 10
-/* Compensate for varying guest execution speed.  */
-static int64_t qemu_icount_bias;
+
+/* Only written by TCG thread */
+static int64_t qemu_icount;
+
 static QEMUTimer *icount_rt_timer;
 static QEMUTimer *icount_vm_timer;
 static QEMUTimer *icount_warp_timer;
-static int64_t vm_clock_warp_start;
-static int64_t qemu_icount;
 
 typedef struct TimersState {
     int64_t cpu_ticks_prev;
@@ -232,6 +237,8 @@  static void icount_adjust(void)
     int64_t cur_time;
     int64_t cur_icount;
     int64_t delta;
+
+    /* Protected by TimersState mutex.  */
     static int64_t last_delta;
 
     /* If the VM is not running, then do nothing.  */