[lustre-devel] [PATCH 23/34] lnet: don't need lock to test ln_shutdown.

[NeilBrown]

On Wed, Sep 12 2018, Doug Oucharek wrote:

> It seems the selection code being affected by this patch later gets moved to its own routine called lnet_select_pathway().  The logic is completely re-written so it may not be important to fix the use of locks here.  However,  it is not good that the lock is not being held while checking for shutdown.

Thanks... I might drop the patch here, and probably fold it into which
ever subsequent patch changes this code can gets rid of lnet_send().

I'll try that anyway.

NeilBrown


>
> Reviewed-by: Doug Oucharek <dougso at me.com>
>
> Doug
>
> On 9/6/18, 5:54 PM, "NeilBrown" <neilb at suse.com> wrote:
>
>     ln_shutdown returns -ESHUTDOWN if ln_shutdown
>     is already set.
>     The lock is always taken to set ln_shutdown, but apparently
>     we don't need to hold the lock for this test.
>     I guess if it is set immediately after the test, and before
>     we take the lock then.... can anything bad happen?
>     
>     This is part of
>         8cbb8cd3e771e7f7e0f99cafc19fad32770dc015
>            LU-7734 lnet: Multi-Rail local NI split
>     
>     Signed-off-by: NeilBrown <neilb at suse.com>
>     ---
>      drivers/staging/lustre/lnet/lnet/lib-move.c |    7 ++-----
>      1 file changed, 2 insertions(+), 5 deletions(-)
>     
>     diff --git a/drivers/staging/lustre/lnet/lnet/lib-move.c b/drivers/staging/lustre/lnet/lnet/lib-move.c
>     index 60f34c4b85d3..46e593fbb44f 100644
>     --- a/drivers/staging/lustre/lnet/lnet/lib-move.c
>     +++ b/drivers/staging/lustre/lnet/lnet/lib-move.c
>     @@ -1099,12 +1099,9 @@ lnet_send(lnet_nid_t src_nid, struct lnet_msg *msg, lnet_nid_t rtr_nid)
>      	cpt = lnet_cpt_of_nid(rtr_nid == LNET_NID_ANY ? dst_nid : rtr_nid,
>      			      local_ni);
>       again:
>     -	lnet_net_lock(cpt);
>     -
>     -	if (the_lnet.ln_shutdown) {
>     -		lnet_net_unlock(cpt);
>     +	if (the_lnet.ln_shutdown)
>      		return -ESHUTDOWN;
>     -	}
>     +	lnet_net_lock(cpt);
>      
>      	if (src_nid == LNET_NID_ANY) {
>      		src_ni = NULL;
>     
>     
>     
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