svn commit: r326964 - head/sys/cam

[Mark Johnston]

On Tue, Dec 19, 2017 at 04:13:22AM +0000, Warner Losh wrote:
> Author: imp
> Date: Tue Dec 19 04:13:22 2017
> New Revision: 326964
> URL: https://svnweb.freebsd.org/changeset/base/326964
> 
> Log:
>   When doing a dump, the scheduler is normally not running, so this
>   changed worked to capture dumps for me. However, the test for
>   SCHEDULER_STOPPED() isn't right. We can also call the dump routine
>   from ddb, in which case the scheduler is still running. This leads to
>   an assertion panic that we're sleeping when we shouldn't. Instead, use
>   the proper test for dumping or not. This brings us in line with other
>   places that do special things while we're doing polled I/O like this.
>   
>   Noticed by: pho@
>   Differential Revision: https://reviews.freebsd.org/D13531
> 
> Modified:
>   head/sys/cam/cam_periph.c
> 
> Modified: head/sys/cam/cam_periph.c
> ==============================================================================
> --- head/sys/cam/cam_periph.c	Tue Dec 19 04:06:07 2017	(r326963)
> +++ head/sys/cam/cam_periph.c	Tue Dec 19 04:13:22 2017	(r326964)
> @@ -38,6 +38,7 @@ __FBSDID("$FreeBSD$");
>  #include <sys/malloc.h>
>  #include <sys/kernel.h>
>  #include <sys/bio.h>
> +#include <sys/conf.h>
>  #include <sys/lock.h>
>  #include <sys/mutex.h>
>  #include <sys/buf.h>
> @@ -1158,7 +1159,7 @@ cam_periph_runccb(union ccb *ccb,
>  	struct bintime *starttime;
>  	struct bintime ltime;
>  	int error;
> -	bool sched_stopped;
> +	bool must_poll;
>  	struct mtx *periph_mtx;
>  	struct cam_periph *periph;
>  	uint32_t timeout = 1;
> @@ -1182,7 +1183,13 @@ cam_periph_runccb(union ccb *ccb,
>  		devstat_start_transaction(ds, starttime);
>  	}
>  
> -	sched_stopped = SCHEDULER_STOPPED();
> +	/*
> +	 * We must poll the I/O while we're dumping. The scheduler is normally
> +	 * stopped for dumping, except when we call doadump from ddb. While the
> +	 * scheduler is running in this case, we still need to poll the I/O to
> +	 * avoid sleeping waiting for the ccb to complete.
> +	 */
> +	must_poll = dumping;

Hmm, unfortunately this introduces a new problem: after a panic we call
adashutdown() as part of the shutdown_post_sync event. This occurs
before we call doadump(), so dumping == 0 and we don't poll for the
spindown command's completion. But since we've panicked, the scheduler
is stopped, and so we just hang.