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tcg: remove global exit_request
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. As an cpu->exit_request may legitimately get squashed while processing the EXCP_INTERRUPT exception we also check cpu->queued_work_first to ensure queued work is expedited as soon as possible. Signed-off-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Richard Henderson <rth@twiddle.net>
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@ -23,8 +23,6 @@
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#include "exec/exec-all.h"
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#include "exec/exec-all.h"
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#include "exec/memory-internal.h"
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#include "exec/memory-internal.h"
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bool exit_request;
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/* exit the current TB, but without causing any exception to be raised */
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/* exit the current TB, but without causing any exception to be raised */
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void cpu_loop_exit_noexc(CPUState *cpu)
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void cpu_loop_exit_noexc(CPUState *cpu)
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{
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{
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20
cpu-exec.c
20
cpu-exec.c
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@ -568,15 +568,13 @@ static inline void cpu_loop_exec_tb(CPUState *cpu, TranslationBlock *tb,
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*tb_exit = ret & TB_EXIT_MASK;
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*tb_exit = ret & TB_EXIT_MASK;
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switch (*tb_exit) {
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switch (*tb_exit) {
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case TB_EXIT_REQUESTED:
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case TB_EXIT_REQUESTED:
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/* Something asked us to stop executing
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/* Something asked us to stop executing chained TBs; just
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* chained TBs; just continue round the main
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* continue round the main loop. Whatever requested the exit
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* loop. Whatever requested the exit will also
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* will also have set something else (eg interrupt_request)
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* have set something else (eg exit_request or
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* which we will handle next time around the loop. But we
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* interrupt_request) which we will handle
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* need to ensure the tcg_exit_req read in generated code
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* next time around the loop. But we need to
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* comes before the next read of cpu->exit_request or
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* ensure the zeroing of tcg_exit_req (see cpu_tb_exec)
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* cpu->interrupt_request.
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* comes before the next read of cpu->exit_request
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* or cpu->interrupt_request.
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*/
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*/
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smp_mb();
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smp_mb();
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*last_tb = NULL;
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*last_tb = NULL;
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@ -630,10 +628,6 @@ int cpu_exec(CPUState *cpu)
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rcu_read_lock();
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rcu_read_lock();
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if (unlikely(atomic_mb_read(&exit_request))) {
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cpu->exit_request = 1;
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}
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cc->cpu_exec_enter(cpu);
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cc->cpu_exec_enter(cpu);
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/* Calculate difference between guest clock and host clock.
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/* Calculate difference between guest clock and host clock.
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19
cpus.c
19
cpus.c
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@ -793,7 +793,6 @@ static inline int64_t qemu_tcg_next_kick(void)
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static void qemu_cpu_kick_rr_cpu(void)
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static void qemu_cpu_kick_rr_cpu(void)
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{
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{
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CPUState *cpu;
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CPUState *cpu;
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atomic_mb_set(&exit_request, 1);
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do {
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do {
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cpu = atomic_mb_read(&tcg_current_rr_cpu);
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cpu = atomic_mb_read(&tcg_current_rr_cpu);
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if (cpu) {
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if (cpu) {
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@ -1316,11 +1315,11 @@ static void *qemu_tcg_cpu_thread_fn(void *arg)
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start_tcg_kick_timer();
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start_tcg_kick_timer();
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/* process any pending work */
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atomic_mb_set(&exit_request, 1);
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cpu = first_cpu;
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cpu = first_cpu;
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/* process any pending work */
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cpu->exit_request = 1;
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while (1) {
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while (1) {
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/* Account partial waits to QEMU_CLOCK_VIRTUAL. */
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/* Account partial waits to QEMU_CLOCK_VIRTUAL. */
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qemu_account_warp_timer();
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qemu_account_warp_timer();
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@ -1329,7 +1328,8 @@ static void *qemu_tcg_cpu_thread_fn(void *arg)
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cpu = first_cpu;
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cpu = first_cpu;
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}
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}
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for (; cpu != NULL && !exit_request; cpu = CPU_NEXT(cpu)) {
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while (cpu && !cpu->queued_work_first && !cpu->exit_request) {
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atomic_mb_set(&tcg_current_rr_cpu, cpu);
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atomic_mb_set(&tcg_current_rr_cpu, cpu);
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qemu_clock_enable(QEMU_CLOCK_VIRTUAL,
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qemu_clock_enable(QEMU_CLOCK_VIRTUAL,
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@ -1349,12 +1349,15 @@ static void *qemu_tcg_cpu_thread_fn(void *arg)
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break;
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break;
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}
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}
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} /* for cpu.. */
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cpu = CPU_NEXT(cpu);
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} /* while (cpu && !cpu->exit_request).. */
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/* Does not need atomic_mb_set because a spurious wakeup is okay. */
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/* Does not need atomic_mb_set because a spurious wakeup is okay. */
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atomic_set(&tcg_current_rr_cpu, NULL);
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atomic_set(&tcg_current_rr_cpu, NULL);
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/* Pairs with smp_wmb in qemu_cpu_kick. */
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if (cpu && cpu->exit_request) {
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atomic_mb_set(&exit_request, 0);
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atomic_mb_set(&cpu->exit_request, 0);
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}
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handle_icount_deadline();
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handle_icount_deadline();
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@ -404,7 +404,4 @@ bool memory_region_is_unassigned(MemoryRegion *mr);
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/* vl.c */
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/* vl.c */
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extern int singlestep;
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extern int singlestep;
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/* cpu-exec.c, accessed with atomic_mb_read/atomic_mb_set */
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extern bool exit_request;
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#endif
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#endif
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