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fix race that can give duplicate host number

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Just once, two fcoe instances got the same host number
from scsi_add_host().

Use atomic_t and atomic_inc_return() to get next host number.
Subtract 1, so that scsi_host still starts with 0.

[jejb: added comment about unusual subtraction]
Signed-off-by: Joe Eykholt <jeykholt@cisco.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
This commit is contained in:
Joe Eykholt 2009-06-15 23:22:14 -07:00 committed by James Bottomley
parent 1119865935
commit 30c9afa6cc
1 changed files with 6 additions and 2 deletions
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8
drivers/scsi/hosts.c
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@ -40,7 +40,7 @@
#include "scsi_logging.h"
static int scsi_host_next_hn; /* host_no for next new host */
static atomic_t scsi_host_next_hn; /* host_no for next new host */
static void scsi_host_cls_release(struct device *dev)
@ -333,7 +333,11 @@ struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize)
mutex_init(&shost->scan_mutex);
shost->host_no = scsi_host_next_hn++; /* XXX(hch): still racy */
/*
* subtract one because we increment first then return, but we need to
* know what the next host number was before increment
*/
shost->host_no = atomic_inc_return(&scsi_host_next_hn) - 1;
shost->dma_channel = 0xff;
/* These three are default values which can be overridden */