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Date:      Wed, 27 Feb 2013 14:53:43 +0100
From:      Hans Petter Selasky <hps@bitfrost.no>
To:        freebsd-acpi@freebsd.org
Subject:   ACPI locking bugs?
Message-ID:  <201302271453.43985.hps@bitfrost.no>
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Hi,

What is the reason for using cv_wait_sig() and cv_timedwait_sig() instead of 
cv_wait() and cv_timedwait() inside of AcpiOsWaitSemaphore(). What signals are 
supposed to be catched here?

       switch (Timeout) {
        case ACPI_DO_NOT_WAIT:
                if (!ACPISEM_AVAIL(as, Units))
                        status = AE_TIME;
                break;
        case ACPI_WAIT_FOREVER:
                while (!ACPISEM_AVAIL(as, Units)) {
                        as->as_waiters++;
                        error = cv_wait_sig(&as->as_cv, &as->as_lock);
                        as->as_waiters--;
                        if (error == EINTR || as->as_reset) {
                                status = AE_ERROR;
                                break;
                        }
                }
                break;
        default:
                tmo = timeout2hz(Timeout);
                while (!ACPISEM_AVAIL(as, Units)) {
                        prevtick = ticks;
                        as->as_waiters++;
                        error = cv_timedwait_sig(&as->as_cv, &as->as_lock, 
tmo);
                        as->as_waiters--;
                        if (error == EINTR || as->as_reset) {
                                status = AE_ERROR;
                                break;
                        }
                        if (ACPISEM_AVAIL(as, Units))
                                break;
                        slptick = ticks - prevtick;
                        if (slptick >= tmo || slptick < 0) {
                                status = AE_TIME;
                                break;
                        }
                        tmo -= slptick;
                }
        }

I've observed an issue twice on my MacBookPro that some ACPI locking fails 
during shutdown on 9-stable and then the power-off won't complete. I've been 
unable to capture the full dmesg, because syslogd is killed at the moment this 
happens. There are two ACPI error printouts about failed locking.

I see that in the case of ACPI_WAIT_FOREVER, it appears to be incorrect to 
catch signals, because sometimes the return argument is not checked for lock 
operations:

./components/utilities/utosi.c:    (void) AcpiOsAcquireMutex 
(AcpiGbl_OsiMutex, ACPI_WAIT_FOREVER);
./components/utilities/utosi.c:    (void) AcpiOsAcquireMutex 
(AcpiGbl_OsiMutex, ACPI_WAIT_FOREVER);
./components/utilities/utosi.c:    (void) AcpiOsAcquireMutex 
(AcpiGbl_OsiMutex, ACPI_WAIT_FOREVER);

Any comments?

Reference: sys/dev/acpica/Osd/OsdSynch.c:AcpiOsWaitSemaphore

--HPS

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