Commit 027d9a7d authored by Alex Bennée's avatar Alex Bennée Committed by Paolo Bonzini
Browse files

cpu: atomically modify cpu->exit_request 



ThreadSanitizer picks up potential races although we already use
barriers to ensure things are in the correct order when processing exit
requests. For true C11 defined behaviour across threads we need to use
relaxed atomic_set/atomic_read semantics to reassure tsan.

Signed-off-by: default avatarAlex Bennée <alex.bennee@linaro.org>
Message-Id: <20160930213106.20186-9-alex.bennee@linaro.org>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent ce7cf6a9

cpu-exec.c

+4 −4
Original line number Diff line number Diff line
@@ -192,7 +192,7 @@ static inline tcg_target_ulong cpu_tb_exec(CPUState *cpu, TranslationBlock *itb) 
        /* We were asked to stop executing TBs (probably a pending

         * interrupt. We've now stopped, so clear the flag.

         */

        cpu->tcg_exit_req = 0;

        atomic_set(&cpu->tcg_exit_req, 0);

    }

    return ret;

}
@@ -490,8 +490,8 @@ static inline void cpu_handle_interrupt(CPUState *cpu, 
            *last_tb = NULL;

        }

    }

    if (unlikely(cpu->exit_request || replay_has_interrupt())) {

        cpu->exit_request = 0;

    if (unlikely(atomic_read(&cpu->exit_request) || replay_has_interrupt())) {

        atomic_set(&cpu->exit_request, 0);

        cpu->exception_index = EXCP_INTERRUPT;

        cpu_loop_exit(cpu);

    }
@@ -503,7 +503,7 @@ static inline void cpu_loop_exec_tb(CPUState *cpu, TranslationBlock *tb, 
{

    uintptr_t ret;



    if (unlikely(cpu->exit_request)) {

    if (unlikely(atomic_read(&cpu->exit_request))) {

        return;

    }

qom/cpu.c

+2 −2
Original line number Diff line number Diff line
@@ -120,10 +120,10 @@ void cpu_reset_interrupt(CPUState *cpu, int mask) 


void cpu_exit(CPUState *cpu)

{

    cpu->exit_request = 1;

    atomic_set(&cpu->exit_request, 1);

    /* Ensure cpu_exec will see the exit request after TCG has exited.  */

    smp_wmb();

    cpu->tcg_exit_req = 1;

    atomic_set(&cpu->tcg_exit_req, 1);

}



int cpu_write_elf32_qemunote(WriteCoreDumpFunction f, CPUState *cpu,