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Re: [Qemu-devel] [3/4] cpus: protect TimerState writes with a spinlock
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [3/4] cpus: protect TimerState writes with a spinlock |
Date: |
Mon, 10 Sep 2018 14:59:27 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 |
On 10/09/2018 07:36, Pavel Dovgalyuk wrote:
> After locking here,
>
>> if (runstate_is_running()) {
>> int64_t clock = REPLAY_CLOCK(REPLAY_CLOCK_VIRTUAL_RT,
>> cpu_get_clock_locked());
> REPLAY_CLOCK can't request icount with cpu_get_icount_raw, because
> it loops infinitely here:
>
> do {
> start = seqlock_read_begin(&timers_state.vm_clock_seqlock);
> icount = cpu_get_icount_raw_locked();
> } while (seqlock_read_retry(&timers_state.vm_clock_seqlock, start));
Yeah, I meant to ask for the backtrace but I can see that the issue is in
replay_save_instructions(). Does this work?
diff --git a/cpus.c b/cpus.c
index 8ee6e5db93..f257a6ef12 100644
--- a/cpus.c
+++ b/cpus.c
@@ -502,8 +502,8 @@ static void icount_warp_rt(void)
seqlock_write_lock(&timers_state.vm_clock_seqlock,
&timers_state.vm_clock_lock);
if (runstate_is_running()) {
- int64_t clock = REPLAY_CLOCK(REPLAY_CLOCK_VIRTUAL_RT,
- cpu_get_clock_locked());
+ int64_t clock = REPLAY_CLOCK_LOCKED(REPLAY_CLOCK_VIRTUAL_RT,
+ cpu_get_clock_locked());
int64_t warp_delta;
warp_delta = clock - timers_state.vm_clock_warp_start;
diff --git a/include/sysemu/replay.h b/include/sysemu/replay.h
index 3ced6bc231..bb8660b4e4 100644
--- a/include/sysemu/replay.h
+++ b/include/sysemu/replay.h
@@ -100,14 +100,20 @@ bool replay_has_interrupt(void);
/* Processing clocks and other time sources */
/*! Save the specified clock */
-int64_t replay_save_clock(ReplayClockKind kind, int64_t clock);
+int64_t replay_save_clock(ReplayClockKind kind, int64_t clock,
+ int64_t raw_icount);
/*! Read the specified clock from the log or return cached data */
int64_t replay_read_clock(ReplayClockKind kind);
/*! Saves or reads the clock depending on the current replay mode. */
#define REPLAY_CLOCK(clock, value) \
(replay_mode == REPLAY_MODE_PLAY ? replay_read_clock((clock)) \
: replay_mode == REPLAY_MODE_RECORD \
- ? replay_save_clock((clock), (value)) \
+ ? replay_save_clock((clock), (value), cpu_get_icount_raw()) \
+ : (value))
+#define REPLAY_CLOCK_LOCKED(clock, value) \
+ (replay_mode == REPLAY_MODE_PLAY ? replay_read_clock((clock)) \
+ : replay_mode == REPLAY_MODE_RECORD \
+ ? replay_save_clock((clock), (value), cpu_get_icount_raw_locked())
\
: (value))
/* Events */
diff --git a/replay/replay-internal.c b/replay/replay-internal.c
index b077cb5fd5..7be4c010d0 100644
--- a/replay/replay-internal.c
+++ b/replay/replay-internal.c
@@ -217,20 +217,25 @@ void replay_mutex_unlock(void)
}
}
+void replay_advance_current_step(uint64_t current_step)
+{
+ int diff = (int)(current_step - replay_state.current_step);
+
+ /* Time can only go forward */
+ assert(diff >= 0);
+
+ if (diff > 0) {
+ replay_put_event(EVENT_INSTRUCTION);
+ replay_put_dword(diff);
+ replay_state.current_step += diff;
+ }
+}
+
/*! Saves cached instructions. */
void replay_save_instructions(void)
{
if (replay_file && replay_mode == REPLAY_MODE_RECORD) {
g_assert(replay_mutex_locked());
- int diff = (int)(replay_get_current_step() -
replay_state.current_step);
-
- /* Time can only go forward */
- assert(diff >= 0);
-
- if (diff > 0) {
- replay_put_event(EVENT_INSTRUCTION);
- replay_put_dword(diff);
- replay_state.current_step += diff;
- }
+ replay_advance_current_step(replay_get_current_step());
}
}
diff --git a/replay/replay-internal.h b/replay/replay-internal.h
index ac4b27b674..4f82676209 100644
--- a/replay/replay-internal.h
+++ b/replay/replay-internal.h
@@ -122,6 +122,8 @@ void replay_finish_event(void);
data_kind variable. */
void replay_fetch_data_kind(void);
+/*! Advance replay_state.current_step to the specified value. */
+void replay_advance_current_step(uint64_t current_step);
/*! Saves queued events (like instructions and sound). */
void replay_save_instructions(void);
diff --git a/replay/replay-time.c b/replay/replay-time.c
index 6a7565ec8d..17caf35e74 100644
--- a/replay/replay-time.c
+++ b/replay/replay-time.c
@@ -15,13 +15,15 @@
#include "replay-internal.h"
#include "qemu/error-report.h"
-int64_t replay_save_clock(ReplayClockKind kind, int64_t clock)
+int64_t replay_save_clock(ReplayClockKind kind, int64_t clock, int64_t
raw_icount)
{
-
if (replay_file) {
g_assert(replay_mutex_locked());
- replay_save_instructions();
+ /* Due to the caller's locking requirements we get the icount from it
instead
+ * of using replay_save_instructions().
+ */
+ replay_advance_current_step(raw_icount);
replay_put_event(EVENT_CLOCK + kind);
replay_put_qword(clock);
}
Thanks,
Paolo