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- The entire receive queue can be used again instead of only SRPT_RQ_SIZE - 1
  elements (as in r1470).
- Added initiator-lockup-avoidance code to SRP_TSK_MGMT processing code too.


git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@1473 d57e44dd-8a1f-0410-8b47-8ef2f437770f
This commit is contained in:
Bart Van Assche
2010-01-17 13:07:46 +00:00
parent 5ce3870372
commit 421dbafa7c
1 changed files with 29 additions and 17 deletions
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46
srpt/src/ib_srpt.c
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@@ -2596,15 +2596,29 @@ out:
/**
* srpt_must_wait_for_cred() - Whether or not the target must wait with
* sending a response towards the initiator in order to avoid that the
* initiator locks up. Since an initiator must not send an SRP_CMD request
* when its req_lim variable is less than 2, and since sending a response to
* the initiator will make its req_lim variable equal to ch->req_lim, do not
* send a response to the initiator that would make its req_lim variable less
* than 2.
* initiator locks up. The Linux SRP initiator locks up when:
* initiator.req_lim < req_lim_min (2 for SRP_CMD; 1 for SRP_TSK_MGMT).
* no new SRP_RSP is received, or new SRP_RSP do not increase initiator.req_lim.
* In order to avoid an initiator lock up, the target must not send an SRP_RSP
* that keeps initiator.req_lim < req_lim_min when initiator.req_lim
* < req_lim_min. when target.req_lim == req_lim_min - 1, initiator.req_lim must
* also equal req_lim_min - 1 because of the credit mechanism defined in the
* SRP standard. Hence wait with sending a response if that response would not
* increase initiator.req_lim.
*/
static inline bool srpt_must_wait_for_cred(struct srpt_rdma_ch *ch)
static bool srpt_must_wait_for_cred(struct srpt_rdma_ch *ch, int req_lim_min)
{
return atomic_read(&ch->req_lim) < 2;
int req_lim;
req_lim = atomic_read(&ch->req_lim);
return req_lim < req_lim_min
&& req_lim - atomic_read(&ch->last_response_req_lim) + 1 <= 0;
}
static void srpt_wait_for_cred(struct srpt_rdma_ch *ch, int req_lim_min)
{
while (unlikely(srpt_must_wait_for_cred(ch, req_lim_min)))
schedule();
}
/**
@@ -2636,16 +2650,13 @@ static int srpt_xmit_response(struct scst_cmd *scmnd)
goto out;
}
if (srpt_must_wait_for_cred(ch)) {
if (scst_cmd_atomic(scmnd)) {
TRACE_DBG("%s", "Switching to thread context.");
ret = SCST_TGT_RES_NEED_THREAD_CTX;
goto out;
}
while (srpt_must_wait_for_cred(ch))
schedule();
if (unlikely(scst_cmd_atomic(scmnd))) {
TRACE_DBG("%s", "Switching to thread context.");
ret = SCST_TGT_RES_NEED_THREAD_CTX;
goto out;
}
srpt_wait_for_cred(ch, 2);
if (srpt_set_cmd_state(ioctx, SRPT_STATE_PROCESSED)
== SRPT_STATE_ABORTED) {
@@ -2715,8 +2726,9 @@ static void srpt_tsk_mgmt_done(struct scst_mgmt_cmd *mcmnd)
__func__, (unsigned long long)mgmt_ioctx->tag,
scst_mgmt_cmd_get_status(mcmnd));
if (atomic_read(&ch->req_lim) < 1)
PRINT_ERROR("%s", "Initiator may lock up !!");
WARN_ON(in_irq());
srpt_wait_for_cred(ch, 1);
if (srpt_set_cmd_state(ioctx, SRPT_STATE_PROCESSED)
== SRPT_STATE_ABORTED)