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Increased SRP initiator lockup safety margin, fixed a sparse warning and added more comments.

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git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@1869 d57e44dd-8a1f-0410-8b47-8ef2f437770f
This commit is contained in:
Bart Van Assche
2010-07-23 13:41:55 +00:00
parent 7322ff6c24
commit 06b4f6d8aa
1 changed files with 22 additions and 7 deletions
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srpt/src/ib_srpt.c
+22 -7
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@@ -1064,20 +1064,21 @@ out:
* been called. This value is necessary for filling in the REQUEST LIMIT DELTA
* field of an SRP_RSP response.
*
* Side Effect: Modifies ch->last_response_req_lim.
* Side Effect:
* Increases ch->last_response_req_lim by 'delta', the value returned.
*/
static int srpt_req_lim_delta(struct srpt_rdma_ch *ch)
{
int req_lim;
unsigned long flags;
int res;
int delta;
req_lim = atomic_read(&ch->req_lim);
spin_lock_irqsave(&ch->cred_lock, flags);
res = req_lim - ch->last_response_req_lim;
delta = req_lim - ch->last_response_req_lim;
ch->last_response_req_lim = req_lim;
spin_unlock_irqrestore(&ch->cred_lock, flags);
return res;
return delta;
}
/**
@@ -3098,14 +3099,19 @@ out:
* req_lim_min if that response would not increase initiator.req_lim. The last
* condition is equivalent to srpt_req_lim_delta(ch) + 1 <= 0.
*
* See also: For more information about how to reproduce the initiator lockup,
* see also http://bugzilla.kernel.org/show_bug.cgi?id=14235.
* If this function returns false, the caller must either send a response to
* the initiator with the REQUEST LIMIT DELTA field set to delta + 1 or call
* srpt_undo_req_lim_delta(ch, delta); where delta is the value written to
* the address that is the third argument of this function.
*
* Note: The constant 'compensate_for_incoming_requests' compensates for the
* fact that if the initiator uses an I/O depth that is larger than one,
* req_lim may have decreased towards req_lim_min after this function returned
* and before the initiator has received and processed the SRP_RSP whose
* REQUEST LIMIT DELTA field will have been set to *req_lim_delta.
*
* See also: For more information about how to reproduce the initiator lockup,
* see also http://bugzilla.kernel.org/show_bug.cgi?id=14235.
*/
static bool srpt_must_wait_for_cred(struct srpt_rdma_ch *ch, int req_lim_min,
int *req_lim_delta)
@@ -3114,7 +3120,7 @@ static bool srpt_must_wait_for_cred(struct srpt_rdma_ch *ch, int req_lim_min,
int delta;
unsigned long flags;
bool res;
enum { compensate_for_incoming_requests = 1 };
enum { compensate_for_incoming_requests = 3 };
EXTRACHECKS_BUG_ON(!req_lim_delta);
@@ -3136,10 +3142,19 @@ static bool srpt_must_wait_for_cred(struct srpt_rdma_ch *ch, int req_lim_min,
return res;
}
/**
* srpt_wait_for_cred() - Wait until sending a response won't lock up the
* initiator.
*
* The caller must either send a response to the initiator with the REQUEST
* LIMIT DELTA field set to delta + 1 or call srpt_undo_req_lim_delta(ch,
* delta); where delta is the return value of this function.
*/
static int srpt_wait_for_cred(struct srpt_rdma_ch *ch, int req_lim_min)
{
int delta;
delta = 0; /* superfluous -- to keep sparse happy */
while (unlikely(srpt_must_wait_for_cred(ch, req_lim_min, &delta)))
schedule();
return delta;