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[Qemu-devel] [RFC v4 18/28] tcg: remove global exit_request
From: |
Alex Bennée |
Subject: |
[Qemu-devel] [RFC v4 18/28] tcg: remove global exit_request |
Date: |
Thu, 11 Aug 2016 16:24:14 +0100 |
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>
---
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 | 1 -
cpu-exec.c | 9 ++-------
cpus.c | 18 ++++++++++--------
include/exec/exec-all.h | 1 -
4 files changed, 12 insertions(+), 17 deletions(-)
diff --git a/cpu-exec-common.c b/cpu-exec-common.c
index e220ba7..e29cf6d 100644
--- a/cpu-exec-common.c
+++ b/cpu-exec-common.c
@@ -23,7 +23,6 @@
#include "exec/exec-all.h"
#include "exec/memory-internal.h"
-bool exit_request;
int tcg_pending_threads;
/* exit the current TB, but without causing any exception to be raised */
diff --git a/cpu-exec.c b/cpu-exec.c
index 317ad8e..d2e8b9e 100644
--- a/cpu-exec.c
+++ b/cpu-exec.c
@@ -531,9 +531,8 @@ 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.
@@ -589,10 +588,6 @@ 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 5ed6dc0..8a40a08 100644
--- a/cpus.c
+++ b/cpus.c
@@ -1215,7 +1215,6 @@ static CPUState *tcg_current_rr_cpu;
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) {
@@ -1265,11 +1264,11 @@ static void *qemu_tcg_cpu_thread_fn(void *arg)
timer_mod(kick_timer, qemu_tcg_next_kick());
}
- /* 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();
@@ -1278,7 +1277,7 @@ 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,
@@ -1300,12 +1299,15 @@ 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 3547dfa..27d1a24 100644
--- a/include/exec/exec-all.h
+++ b/include/exec/exec-all.h
@@ -409,7 +409,6 @@ extern int singlestep;
/* cpu-exec.c, accessed with atomic_mb_read/atomic_mb_set */
extern int tcg_pending_threads;
-extern bool exit_request;
/**
* qemu_work_cond - condition to wait for CPU work items completion
--
2.7.4
- [Qemu-devel] [RFC v4 10/28] target-arm/arm-powerctl: wake up sleeping CPUs, (continued)
- [Qemu-devel] [RFC v4 10/28] target-arm/arm-powerctl: wake up sleeping CPUs, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 07/28] linux-user/elfload: ensure mmap_lock() held while setting up, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 06/28] tcg: comment on which functions have to be called with tb_lock held, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 15/28] tcg: rename tcg_current_cpu to tcg_current_rr_cpu, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 09/28] tcg: protect TBContext with tb_lock., Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 11/28] tcg: move tcg_exec_all and helpers above thread fn, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 14/28] tcg: add kick timer for single-threaded vCPU emulation, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 12/28] tcg: cpus rm tcg_exec_all(), Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 13/28] tcg: add options for enabling MTTCG, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 17/28] cpus: re-factor out handle_icount_deadline, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 18/28] tcg: remove global exit_request,
Alex Bennée <=
- [Qemu-devel] [RFC v4 19/28] tcg: move locking for tb_invalidate_phys_page_range up, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 16/28] tcg: drop global lock during TCG code execution, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 21/28] tcg: enable tb_lock() for SoftMMU, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 22/28] tcg: enable thread-per-vCPU, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 25/28] cputlb: introduce tlb_flush_* async work., Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 23/28] atomic: introduce cmpxchg_bool, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 24/28] cputlb: add assert_cpu_is_self checks, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 26/28] cputlb: tweak qemu_ram_addr_from_host_nofail reporting, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 20/28] cpus: tweak sleeping and safe_work rules for MTTCG, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 28/28] cputlb: make tlb_flush_by_mmuidx safe for MTTCG, Alex Bennée, 2016/08/11