Re: [PATCH 10/10] FIX: wait_backup() sometimes hungs

[Neil Brown <neilb@suse.de>]

On Thu, 02 Dec 2010 09:19:58 +0100 Adam Kwolek <adam.kwolek@intel.com> wrote:

> Sometimes wait_backup() omits transition from reshape to iddle state and mdadm seams to be hung.
> Add 1 sec. timeout wor waiting on select. This allows for wait_backup exit when reshape is ended.
> 
> Signed-off-by: Adam Kwolek <adam.kwolek@intel.com>
> ---
> 
>  Grow.c |    6 +++++-
>  1 files changed, 5 insertions(+), 1 deletions(-)
> 
> diff --git a/Grow.c b/Grow.c
> index 24c5c39..e16b1ad 100644
> --- a/Grow.c
> +++ b/Grow.c
> @@ -2074,10 +2074,14 @@ static int wait_backup(struct mdinfo *sra,
>  		sysfs_set_str(sra, NULL, "sync_action", "reshape");
>  	do {
>  		char action[20];
> +		struct timeval t;
> +
> +		t.tv_sec = 1;
> +		t.tv_usec = 0;
>  		fd_set rfds;
>  		FD_ZERO(&rfds);
>  		FD_SET(fd, &rfds);
> -		select(fd+1, NULL, NULL, &rfds, NULL);
> +		select(fd+1, NULL, NULL, &rfds, &t);
>  		if (sysfs_fd_get_ll(fd, &completed) < 0) {
>  			close(fd);
>  			return -1;


Thanks.  However I don't think the 1 second timeout is necessary.  This is
really the same problem as the previous one.  We just need to read
'completed' before the first 'select'.  Like this.

Thanks,
NeilBrown

commit 97bef35459306dfd291f40bc5221ad20ab9c21ba
Author: Adam Kwolek <adam.kwolek@intel.com>
Date:   Fri Dec 3 15:15:51 2010 +1100

    FIX: wait_backup() sometimes hungs
    
    Sometimes wait_backup() omits transition from reshape to idle state
    and mdadm seams to be hung.  So check the 'complete' count
    *before* waiting rather than only after.
    
    Signed-off-by: Adam Kwolek <adam.kwolek@intel.com>
    Signed-off-by: NeilBrown <neilb@suse.de>

diff --git a/Grow.c b/Grow.c
index 3322cf7..99807b4 100644
--- a/Grow.c
+++ b/Grow.c
@@ -2058,12 +2058,17 @@ static int wait_backup(struct mdinfo *sra,
 	sysfs_set_num(sra, NULL, "sync_max", offset + blocks + blocks2);
 	if (offset == 0)
 		sysfs_set_str(sra, NULL, "sync_action", "reshape");
-	do {
+
+	if (sysfs_fd_get_ll(fd, &completed) < 0) {
+		close(fd);
+		return -1;
+	}
+	while (completed < offset + blocks) {
 		char action[20];
 		fd_set rfds;
 		FD_ZERO(&rfds);
 		FD_SET(fd, &rfds);
-		select(fd+1, NULL, NULL, &rfds, NULL);
+		select(fd+1, NULL, NULL, &rfds, &t);
 		if (sysfs_fd_get_ll(fd, &completed) < 0) {
 			close(fd);
 			return -1;
@@ -2072,7 +2077,7 @@ static int wait_backup(struct mdinfo *sra,
 				  action, 20) > 0 &&
 		    strncmp(action, "reshape", 7) != 0)
 			break;
-	} while (completed < offset + blocks);
+	}
 	close(fd);
 
 	if (part) {