[lustre-devel] [PATCH 4/7] lustre: give different tcd_lock types different classes.

[Andreas Dilger <adilger@whamcloud.com>]

On Jul 29, 2018, at 21:49, NeilBrown <neilb@suse.com> wrote:
> 
> There are three different trace contexts:
> process, softirq, irq.
> Each has its own lock (tcd_lock) which is locked
> as appropriate for that context.
> lockdep currently doesn't see that they are different
> and so deduces that the different uses might lead to
> deadlocks.
> So use separate calls to spin_lock_init() so that they
> each get a separate lock class, and lockdep sees no
> problem.
> 
> Signed-off-by: NeilBrown <neilb@suse.com>

Reviewed-by: Andreas Dilger <adilger@whamcloud.com>

> ---
> drivers/staging/lustre/lnet/libcfs/tracefile.c |   18 +++++++++++++++++-
> 1 file changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/lustre/lnet/libcfs/tracefile.c b/drivers/staging/lustre/lnet/libcfs/tracefile.c
> index d4c80cf254e4..40048165fc16 100644
> --- a/drivers/staging/lustre/lnet/libcfs/tracefile.c
> +++ b/drivers/staging/lustre/lnet/libcfs/tracefile.c
> @@ -1285,7 +1285,23 @@ int cfs_tracefile_init(int max_pages)
> 	cfs_tcd_for_each(tcd, i, j) {
> 		int factor = pages_factor[i];
> 
> -		spin_lock_init(&tcd->tcd_lock);
> +		/* Note that we have three separate calls so
> +		 * they the locks get three separate classes
> +		 * and lockdep never thinks they are related.
> +		 * As they are used in different interrupt
> +		 * contexts, lockdep think the usage would conflict.
> +		 */
> +		switch(i) {
> +		case CFS_TCD_TYPE_PROC:
> +			spin_lock_init(&tcd->tcd_lock);
> +			break;
> +		case CFS_TCD_TYPE_SOFTIRQ:
> +			spin_lock_init(&tcd->tcd_lock);
> +			break;
> +		case CFS_TCD_TYPE_IRQ:
> +			spin_lock_init(&tcd->tcd_lock);
> +			break;
> +		}
> 		tcd->tcd_pages_factor = factor;
> 		tcd->tcd_type = i;
> 		tcd->tcd_cpu = j;
> 
> 

Cheers, Andreas
---
Andreas Dilger
CTO Whamcloud




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