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[Qemu-devel] [PATCH v6 06/19] tcg: remove global exit_request
From: |
Alex Bennée |
Subject: |
[Qemu-devel] [PATCH v6 06/19] tcg: remove global exit_request |
Date: |
Wed, 9 Nov 2016 14:57:35 +0000 |
There are now only two uses of the global exit_request left.
The first ensures we exit the run_loop when we first start to process
pending work and in the kick handler. This is just as easily done by
setting the first_cpu->exit_request flag.
The second use is in the round robin kick routine. The global
exit_request ensured every vCPU would set its local exit_request and
cause a full exit of the loop. Now the iothread isn't being held while
running we can just rely on the kick handler to push us out as intended.
We lightly re-factor the main vCPU thread to ensure cpu->exit_requests
cause us to exit the main loop and process any IO requests that might
come along.
Signed-off-by: Alex Bennée <address@hidden>
Reviewed-by: Richard Henderson <address@hidden>
---
v5
- minor merge conflict with kick patch
v4
- moved to after iothread unlocking patch
- needed to remove kick exit_request as well.
- remove extraneous cpu->exit_request check
- remove stray exit_request setting
- remove needless atomic operation
---
cpu-exec-common.c | 2 --
cpu-exec.c | 9 ++-------
cpus.c | 18 ++++++++++--------
include/exec/exec-all.h | 3 ---
4 files changed, 12 insertions(+), 20 deletions(-)
diff --git a/cpu-exec-common.c b/cpu-exec-common.c
index e2bc053..0504a94 100644
--- a/cpu-exec-common.c
+++ b/cpu-exec-common.c
@@ -23,8 +23,6 @@
#include "exec/exec-all.h"
#include "exec/memory-internal.h"
-bool exit_request;
-
/* exit the current TB, but without causing any exception to be raised */
void cpu_loop_exit_noexc(CPUState *cpu)
{
diff --git a/cpu-exec.c b/cpu-exec.c
index 59a9fc4..c4c7a06 100644
--- a/cpu-exec.c
+++ b/cpu-exec.c
@@ -561,9 +561,8 @@ static inline void cpu_loop_exec_tb(CPUState *cpu,
TranslationBlock *tb,
/* Something asked us to stop executing
* chained TBs; just continue round the main
* loop. Whatever requested the exit will also
- * have set something else (eg exit_request or
- * interrupt_request) which we will handle
- * next time around the loop. But we need to
+ * have set something else (eg interrupt_request) which we
+ * will handle next time around the loop. But we need to
* ensure the tcg_exit_req read in generated code
* comes before the next read of cpu->exit_request
* or cpu->interrupt_request.
@@ -619,10 +618,6 @@ int cpu_exec(CPUState *cpu)
rcu_read_lock();
- if (unlikely(atomic_mb_read(&exit_request))) {
- cpu->exit_request = 1;
- }
-
cc->cpu_exec_enter(cpu);
/* Calculate difference between guest clock and host clock.
diff --git a/cpus.c b/cpus.c
index 7116ac6..6d43f32 100644
--- a/cpus.c
+++ b/cpus.c
@@ -761,7 +761,6 @@ static inline int64_t qemu_tcg_next_kick(void)
static void qemu_cpu_kick_rr_cpu(void)
{
CPUState *cpu;
- atomic_mb_set(&exit_request, 1);
do {
cpu = atomic_mb_read(&tcg_current_rr_cpu);
if (cpu) {
@@ -1283,11 +1282,11 @@ static void *qemu_tcg_cpu_thread_fn(void *arg)
start_tcg_kick_timer();
- /* process any pending work */
- atomic_mb_set(&exit_request, 1);
-
cpu = first_cpu;
+ /* process any pending work */
+ cpu->exit_request = 1;
+
while (1) {
/* Account partial waits to QEMU_CLOCK_VIRTUAL. */
qemu_account_warp_timer();
@@ -1296,7 +1295,7 @@ static void *qemu_tcg_cpu_thread_fn(void *arg)
cpu = first_cpu;
}
- for (; cpu != NULL && !exit_request; cpu = CPU_NEXT(cpu)) {
+ while (cpu && !cpu->exit_request) {
atomic_mb_set(&tcg_current_rr_cpu, cpu);
qemu_clock_enable(QEMU_CLOCK_VIRTUAL,
@@ -1316,12 +1315,15 @@ static void *qemu_tcg_cpu_thread_fn(void *arg)
break;
}
- } /* for cpu.. */
+ cpu = CPU_NEXT(cpu);
+ } /* while (cpu && !cpu->exit_request).. */
+
/* Does not need atomic_mb_set because a spurious wakeup is okay. */
atomic_set(&tcg_current_rr_cpu, NULL);
- /* Pairs with smp_wmb in qemu_cpu_kick. */
- atomic_mb_set(&exit_request, 0);
+ if (cpu && cpu->exit_request) {
+ atomic_mb_set(&cpu->exit_request, 0);
+ }
handle_icount_deadline();
diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
index 5a1b3a3..37781e0 100644
--- a/include/exec/exec-all.h
+++ b/include/exec/exec-all.h
@@ -405,7 +405,4 @@ bool memory_region_is_unassigned(MemoryRegion *mr);
/* vl.c */
extern int singlestep;
-/* cpu-exec.c, accessed with atomic_mb_read/atomic_mb_set */
-extern bool exit_request;
-
#endif
--
2.10.1
- Re: [Qemu-devel] [PATCH v6 03/19] tcg: add kick timer for single-threaded vCPU emulation, (continued)
- [Qemu-devel] [PATCH v6 04/19] tcg: rename tcg_current_cpu to tcg_current_rr_cpu, Alex Bennée, 2016/11/09
- [Qemu-devel] [PATCH v6 05/19] tcg: drop global lock during TCG code execution, Alex Bennée, 2016/11/09
- [Qemu-devel] [PATCH v6 09/19] tcg: handle EXCP_ATOMIC exception for system emulation, Alex Bennée, 2016/11/09
- [Qemu-devel] [PATCH v6 02/19] tcg: add options for enabling MTTCG, Alex Bennée, 2016/11/09
- [Qemu-devel] [PATCH v6 08/19] tcg: enable thread-per-vCPU, Alex Bennée, 2016/11/09
- [Qemu-devel] [PATCH v6 06/19] tcg: remove global exit_request,
Alex Bennée <=
- [Qemu-devel] [PATCH v6 12/19] cputlb: tweak qemu_ram_addr_from_host_nofail reporting, Alex Bennée, 2016/11/09
- [Qemu-devel] [PATCH v6 07/19] tcg: enable tb_lock() for SoftMMU, Alex Bennée, 2016/11/09
- [Qemu-devel] [PATCH v6 10/19] cputlb: add assert_cpu_is_self checks, Alex Bennée, 2016/11/09
- [Qemu-devel] [PATCH v6 11/19] cputlb: introduce tlb_flush_* async work., Alex Bennée, 2016/11/09
- [Qemu-devel] [PATCH v6 15/19] target-arm/cpu: don't reset TLB structures, use cputlb to do it, Alex Bennée, 2016/11/09