Re: [patch] Real-Time Preemption, -RT-2.6.9-rc4-mm1-U7
From: Thomas Gleixner
Date: Wed Oct 20 2004 - 05:18:59 EST
On Wed, 2004-10-20 at 09:40, Ingo Molnar wrote:
> > - scsi_error_handler() fix
> > - device subsystem device_remove locking fix
>
> thanks, i've applied these. The block/loop.c assert reported by Rui
> seems to be a similar problem too.
Yep, it's all the same scheme. Most of the offending code uses
MUTEX_LOCKED in an init function and plays the down, and up from a
different context game, which triggers the deadlock/owner verify. Not
hard to fix, but at some places it takes a bit, until you see the
intention of the driver hacker.
The most surprising one was in driver/base. I did not expect that new
2.5/6 code uses those tricks too.
Fixes for aic7xxx and sym53c8xx_2 attached.
tglx
diff --exclude='*~' -urN 2.6.9-rc4-mm1-RT-U7/drivers/scsi/aic7xxx/aic7xxx_osm.c 2.6.9-rc4-mm1-RT-U7-work/drivers/scsi/aic7xxx/aic7xxx_osm.c
--- 2.6.9-rc4-mm1-RT-U7/drivers/scsi/aic7xxx/aic7xxx_osm.c 2004-10-12 09:41:33.000000000 +0200
+++ 2.6.9-rc4-mm1-RT-U7-work/drivers/scsi/aic7xxx/aic7xxx_osm.c 2004-10-20 09:33:59.000000000 +0200
@@ -1873,9 +1873,10 @@
ahc->platform_data->completeq_timer.data = (u_long)ahc;
ahc->platform_data->completeq_timer.function =
(ahc_linux_callback_t *)ahc_linux_thread_run_complete_queue;
- init_MUTEX_LOCKED(&ahc->platform_data->eh_sem);
- init_MUTEX_LOCKED(&ahc->platform_data->dv_sem);
- init_MUTEX_LOCKED(&ahc->platform_data->dv_cmd_sem);
+ init_waitqueue_head(&ahc->platform_data->eh_sem);
+ init_waitqueue_head(&ahc->platform_data->dv_sem);
+ init_waitqueue_head(&ahc->platform_data->dv_cmd_sem);
+ init_completion(&ahc->platform_data->dv_exit);
tasklet_init(&ahc->platform_data->runq_tasklet, ahc_runq_tasklet,
(unsigned long)ahc);
ahc->seltime = (aic7xxx_seltime & 0x3) << 4;
@@ -2156,7 +2157,7 @@
ahc_linux_freeze_simq(ahc);
/* Wake up the DV kthread */
- up(&ahc->platform_data->dv_sem);
+ wake_up(&ahc->platform_data->dv_sem);
}
}
@@ -2169,39 +2170,22 @@
if (ahc->platform_data->dv_pid != 0) {
ahc->platform_data->flags |= AHC_DV_SHUTDOWN;
ahc_unlock(ahc, &s);
- up(&ahc->platform_data->dv_sem);
+ wake_up(&ahc->platform_data->dv_sem);
- /*
- * Use the eh_sem as an indicator that the
- * dv thread is exiting. Note that the dv
- * thread must still return after performing
- * the up on our semaphore before it has
- * completely exited this module. Unfortunately,
- * there seems to be no easy way to wait for the
- * exit of a thread for which you are not the
- * parent (dv threads are parented by init).
- * Cross your fingers...
- */
- down(&ahc->platform_data->eh_sem);
-
- /*
- * Mark the dv thread as already dead. This
- * avoids attempting to kill it a second time.
- * This is necessary because we must kill the
- * DV thread before calling ahc_free() in the
- * module shutdown case to avoid bogus locking
- * in the SCSI mid-layer, but we ahc_free() is
- * called without killing the DV thread in the
- * instance detach case, so ahc_platform_free()
- * calls us again to verify that the DV thread
- * is dead.
- */
- ahc->platform_data->dv_pid = 0;
+ /* Wait until the thread has exited */
+ wait_for_completion(&ahc->platform_data->dv_exit);
} else {
ahc_unlock(ahc, &s);
}
}
+#define AHC_WAIT_FOR_WORK \
+ (ahc->platform_data->flags & (AHC_DV_SHUTDOWN | AHC_DV_ACTIVE))
+#define AHC_WAIT_FOR_SIMQ_EMPTY \
+ (!(ahc->platform_data->flags & AHC_DV_WAIT_SIMQ_EMPTY))
+#define AHC_WAIT_FOR_SIMQ_RELEASE \
+ (!(ahc->platform_data->flags & AHC_DV_WAIT_SIMQ_RELEASE))
+
static int
ahc_linux_dv_thread(void *data)
{
@@ -2235,11 +2219,9 @@
unlock_kernel();
while (1) {
- /*
- * Use down_interruptible() rather than down() to
- * avoid inclusion in the load average.
- */
- down_interruptible(&ahc->platform_data->dv_sem);
+ /* Wait for work */
+ wait_event_interruptible(ahc->platform_data->dv_sem,
+ AHC_WAIT_FOR_WORK);
/* Check to see if we've been signaled to exit */
ahc_lock(ahc, &s);
@@ -2262,7 +2244,8 @@
while (LIST_FIRST(&ahc->pending_scbs) != NULL) {
ahc->platform_data->flags |= AHC_DV_WAIT_SIMQ_EMPTY;
ahc_unlock(ahc, &s);
- down_interruptible(&ahc->platform_data->dv_sem);
+ wait_event_interruptible(ahc->platform_data->dv_sem,
+ AHC_WAIT_FOR_SIMQ_EMPTY);
ahc_lock(ahc, &s);
}
@@ -2273,7 +2256,8 @@
while (AHC_DV_SIMQ_FROZEN(ahc) == 0) {
ahc->platform_data->flags |= AHC_DV_WAIT_SIMQ_RELEASE;
ahc_unlock(ahc, &s);
- down_interruptible(&ahc->platform_data->dv_sem);
+ wait_event_interruptible(ahc->platform_data->dv_sem,
+ AHC_WAIT_FOR_SIMQ_RELEASE);
ahc_lock(ahc, &s);
}
ahc_unlock(ahc, &s);
@@ -2291,7 +2275,9 @@
*/
ahc_linux_release_simq((u_long)ahc);
}
- up(&ahc->platform_data->eh_sem);
+ /* Mark it as gone */
+ ahc->platform_data->dv_pid = 0;
+ complete(&ahc->platform_data->dv_exit);
return (0);
}
@@ -2454,7 +2440,9 @@
#else
spin_unlock_irqrestore(&io_request_lock, s);
#endif
- down_interruptible(&ahc->platform_data->dv_cmd_sem);
+ wait_event_interruptible(ahc->platform_data->dv_cmd_sem,
+ !timer_pending(&cmd->eh_timeout));
+
/*
* Wait for the SIMQ to be released so that DV is the
* only reason the queue is frozen.
@@ -2463,7 +2451,8 @@
while (AHC_DV_SIMQ_FROZEN(ahc) == 0) {
ahc->platform_data->flags |= AHC_DV_WAIT_SIMQ_RELEASE;
ahc_unlock(ahc, &s);
- down_interruptible(&ahc->platform_data->dv_sem);
+ wait_event_interruptible(ahc->platform_data->dv_sem,
+ AHC_WAIT_FOR_SIMQ_RELEASE);
ahc_lock(ahc, &s);
}
ahc_unlock(ahc, &s);
@@ -3404,7 +3393,7 @@
#endif
/* Wake up the state machine */
- up(&ahc->platform_data->dv_cmd_sem);
+ wake_up(&ahc->platform_data->dv_cmd_sem);
}
static void
@@ -4164,7 +4153,7 @@
ahc_set_transaction_status(scb, CAM_CMD_TIMEOUT);
if ((ahc->platform_data->flags & AHC_UP_EH_SEMAPHORE) != 0) {
ahc->platform_data->flags &= ~AHC_UP_EH_SEMAPHORE;
- up(&ahc->platform_data->eh_sem);
+ wake_up(&ahc->platform_data->eh_sem);
}
}
@@ -4174,7 +4163,7 @@
if ((ahc->platform_data->flags & AHC_DV_WAIT_SIMQ_EMPTY) != 0
&& LIST_FIRST(&ahc->pending_scbs) == NULL) {
ahc->platform_data->flags &= ~AHC_DV_WAIT_SIMQ_EMPTY;
- up(&ahc->platform_data->dv_sem);
+ wake_up(&ahc->platform_data->dv_sem);
}
}
@@ -4563,7 +4552,7 @@
ahc_lock(ahc, &s);
if ((ahc->platform_data->flags & AHC_UP_EH_SEMAPHORE) != 0) {
ahc->platform_data->flags &= ~AHC_UP_EH_SEMAPHORE;
- up(&ahc->platform_data->eh_sem);
+ wake_up(&ahc->platform_data->eh_sem);
}
ahc_unlock(ahc, &s);
}
@@ -4600,7 +4589,7 @@
if (AHC_DV_SIMQ_FROZEN(ahc)
&& ((ahc->platform_data->flags & AHC_DV_WAIT_SIMQ_RELEASE) != 0)) {
ahc->platform_data->flags &= ~AHC_DV_WAIT_SIMQ_RELEASE;
- up(&ahc->platform_data->dv_sem);
+ wake_up(&ahc->platform_data->dv_sem);
}
ahc_schedule_runq(ahc);
ahc_unlock(ahc, &s);
@@ -4952,7 +4941,8 @@
timer.function = ahc_linux_sem_timeout;
add_timer(&timer);
printf("Recovery code sleeping\n");
- down(&ahc->platform_data->eh_sem);
+ wait_event(ahc->platform_data->eh_sem,
+ !(ahc->platform_data->flags & AHC_UP_EH_SEMAPHORE));
printf("Recovery code awake\n");
ret = del_timer_sync(&timer);
if (ret == 0) {
diff --exclude='*~' -urN 2.6.9-rc4-mm1-RT-U7/drivers/scsi/aic7xxx/aic7xxx_osm.h 2.6.9-rc4-mm1-RT-U7-work/drivers/scsi/aic7xxx/aic7xxx_osm.h
--- 2.6.9-rc4-mm1-RT-U7/drivers/scsi/aic7xxx/aic7xxx_osm.h 2004-10-12 09:41:33.000000000 +0200
+++ 2.6.9-rc4-mm1-RT-U7-work/drivers/scsi/aic7xxx/aic7xxx_osm.h 2004-10-20 09:31:55.000000000 +0200
@@ -534,11 +534,13 @@
pid_t dv_pid;
struct timer_list completeq_timer;
struct timer_list reset_timer;
- struct semaphore eh_sem;
- struct semaphore dv_sem;
- struct semaphore dv_cmd_sem; /* XXX This needs to be in
- * the target struct
+ wait_queue_head_t eh_sem;
+ wait_queue_head_t dv_sem;
+ wait_queue_head_t dv_cmd_sem; /* XXX This needs to be in
+ * the target struct
*/
+ struct completion dv_exit;
+
struct scsi_device *dv_scsi_dev;
struct Scsi_Host *host; /* pointer to scsi host */
#define AHC_LINUX_NOIRQ ((uint32_t)~0)
diff --exclude='*~' -urN 2.6.9-rc4-mm1-RT-U7/drivers/scsi/sym53c8xx_2/sym_glue.c 2.6.9-rc4-mm1-RT-U7-work/drivers/scsi/sym53c8xx_2/sym_glue.c
--- 2.6.9-rc4-mm1-RT-U7/drivers/scsi/sym53c8xx_2/sym_glue.c 2004-10-12 09:41:38.000000000 +0200
+++ 2.6.9-rc4-mm1-RT-U7-work/drivers/scsi/sym53c8xx_2/sym_glue.c 2004-10-20 10:09:04.000000000 +0200
@@ -135,7 +135,7 @@
* It is allocated on the eh thread stack.
*/
struct sym_eh_wait {
- struct semaphore sem;
+ struct completion done;
struct timer_list timer;
void (*old_done)(struct scsi_cmnd *);
int to_do;
@@ -798,7 +798,7 @@
/* Wake up the eh thread if it wants to sleep */
if (ep->to_do == SYM_EH_DO_WAIT)
- up(&ep->sem);
+ complete(&ep->done);
}
/*
@@ -858,7 +858,7 @@
case SYM_EH_DO_IGNORE:
break;
case SYM_EH_DO_WAIT:
- init_MUTEX_LOCKED(&ep->sem);
+ init_completion(&ep->done);
/* fall through */
case SYM_EH_DO_COMPLETE:
ep->old_done = cmd->scsi_done;
@@ -909,7 +909,7 @@
ep->timed_out = 1; /* Be pessimistic for once :) */
add_timer(&ep->timer);
spin_unlock_irq(np->s.host->host_lock);
- down(&ep->sem);
+ wait_for_completion(&ep->done);
spin_lock_irq(np->s.host->host_lock);
if (ep->timed_out)
sts = -2;