Commit 30c8db0e authored by David Hildenbrand's avatar David Hildenbrand Committed by Cornelia Huck
Browse files

s390x/tcg: fix locking problem with tcg_s390_tod_updated 



tcg_s390_tod_updated() is always called with the iothread being locked
(e.g. from S390TODClass->set() e.g. via HELPER(sck) or on incoming
migration). The helper we call takes the lock itself - bad.

Let's change that by factoring out updating the ckc timer. This now looks
much nicer than having to call a helper from another function.

While touching it we also make sure that env->ckc is updated even if the
new value is -1ULL, for now it would not have been modified in that case.

Reported-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: default avatarDavid Hildenbrand <david@redhat.com>
Message-Id: <20180629170520.13671-1-david@redhat.com>
Reviewed-by: default avatarRichard Henderson <richard.henderson@linaro.org>
Signed-off-by: default avatarCornelia Huck <cohuck@redhat.com>
parent d44444b0

target/s390x/misc_helper.c

+16 −10
Original line number Diff line number Diff line
@@ -149,26 +149,23 @@ uint64_t HELPER(stck)(CPUS390XState *env) 
    return tod.low;

}



/* Set Clock Comparator */

void HELPER(sckc)(CPUS390XState *env, uint64_t time)

static void update_ckc_timer(CPUS390XState *env)

{

    S390TODState *td = s390_get_todstate();

    uint64_t time;



    /* stop the timer and remove pending CKC IRQs */

    timer_del(env->tod_timer);

    qemu_mutex_lock_iothread();

    g_assert(qemu_mutex_iothread_locked());

    env->pending_int &= ~INTERRUPT_EXT_CLOCK_COMPARATOR;

    qemu_mutex_unlock_iothread();



    /* the tod has to exceed the ckc, this can never happen if ckc is all 1's */

    if (time == -1ULL) {

    if (env->ckc == -1ULL) {

        return;

    }



    env->ckc = time;



    /* difference between origins */

    time -= td->base.low;

    time = env->ckc - td->base.low;



    /* nanoseconds */

    time = tod2time(time);
@@ -176,12 +173,21 @@ void HELPER(sckc)(CPUS390XState *env, uint64_t time) 
    timer_mod(env->tod_timer, time);

}



/* Set Clock Comparator */

void HELPER(sckc)(CPUS390XState *env, uint64_t ckc)

{

    env->ckc = ckc;



    qemu_mutex_lock_iothread();

    update_ckc_timer(env);

    qemu_mutex_unlock_iothread();

}



void tcg_s390_tod_updated(CPUState *cs, run_on_cpu_data opaque)

{

    S390CPU *cpu = S390_CPU(cs);

    CPUS390XState *env = &cpu->env;



    helper_sckc(env, env->ckc);

    update_ckc_timer(&cpu->env);

}



/* Set Clock */