Messages in this thread | | | Date | Tue, 17 Jul 2018 13:56:39 +0200 | From | Dominique Martinet <> | Subject | Re: [PATCH v2] net/9p/client.c: fix misuse of spin_lock_irqsave for p9_client lock |
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piaojun wrote on Tue, Jul 17, 2018: > In p9_read_work(), we use spin_lock for client->lock, but misuse > spin_lock_irqsave for it in p9_fid_create(). As p9_client lock won't be > locked in irq context, so spin_lock is enough. And that will improve the > performance.
(I didn't say in v1, but the commit message sounds a bit odd to me, if there is any other change to the patch could you please rephrase it a bit?)
> Rebased on 9p-next.
(Likewise, this should probably go below the '---' mark to not be in the final commit message, 9p-next does not make sense to linux as a whole)
> > Signed-off-by: Jun Piao <piaojun@huawei.com>
Nitpicks aside this still looks good to me, I'm not expert in locking but I believe the conn_cancel stuff in trans_fd is called either from user context or workqueue which also is process context, while the rest comes from user context only.
There *are* common functions called from interrupt context (I see: p9_tag_lookup, p9_client_cb, p9_parse_header) but luckily enough none of these take the lock.
I'll give this one a little bit of time for others to review before picking it up, just in case, but will do if no-one complains.
> --- > net/9p/client.c | 18 ++++++++---------- > net/9p/trans_fd.c | 7 +++---- > 2 files changed, 11 insertions(+), 14 deletions(-) > > diff --git a/net/9p/client.c b/net/9p/client.c > index 30f9aee..f6897ee 100644 > --- a/net/9p/client.c > +++ b/net/9p/client.c > @@ -275,14 +275,14 @@ static struct p9_fcall *p9_fcall_alloc(int alloc_msize) > INIT_LIST_HEAD(&req->req_list); > > idr_preload(GFP_NOFS); > - spin_lock_irq(&c->lock); > + spin_lock(&c->lock); > if (type == P9_TVERSION) > tag = idr_alloc(&c->reqs, req, P9_NOTAG, P9_NOTAG + 1, > GFP_NOWAIT); > else > tag = idr_alloc(&c->reqs, req, 0, P9_NOTAG, GFP_NOWAIT); > req->tc->tag = tag; > - spin_unlock_irq(&c->lock); > + spin_unlock(&c->lock); > idr_preload_end(); > if (tag < 0) > goto free; > @@ -328,13 +328,12 @@ struct p9_req_t *p9_tag_lookup(struct p9_client *c, u16 tag) > */ > static void p9_free_req(struct p9_client *c, struct p9_req_t *r) > { > - unsigned long flags; > u16 tag = r->tc->tag; > > p9_debug(P9_DEBUG_MUX, "clnt %p req %p tag: %d\n", c, r, tag); > - spin_lock_irqsave(&c->lock, flags); > + spin_lock(&c->lock); > idr_remove(&c->reqs, tag); > - spin_unlock_irqrestore(&c->lock, flags); > + spin_unlock(&c->lock); > kfree(r->tc); > kfree(r->rc); > kmem_cache_free(p9_req_cache, r); > @@ -846,10 +845,10 @@ static struct p9_fid *p9_fid_create(struct p9_client *clnt) > fid->fid = 0; > > idr_preload(GFP_KERNEL); > - spin_lock_irq(&clnt->lock); > + spin_lock(&clnt->lock); > ret = idr_alloc_u32(&clnt->fids, fid, &fid->fid, P9_NOFID - 1, > GFP_NOWAIT); > - spin_unlock_irq(&clnt->lock); > + spin_unlock(&clnt->lock); > idr_preload_end(); > > if (!ret) > @@ -862,13 +861,12 @@ static struct p9_fid *p9_fid_create(struct p9_client *clnt) > static void p9_fid_destroy(struct p9_fid *fid) > { > struct p9_client *clnt; > - unsigned long flags; > > p9_debug(P9_DEBUG_FID, "fid %d\n", fid->fid); > clnt = fid->clnt; > - spin_lock_irqsave(&clnt->lock, flags); > + spin_lock(&clnt->lock); > idr_remove(&clnt->fids, fid->fid); > - spin_unlock_irqrestore(&clnt->lock, flags); > + spin_unlock(&clnt->lock); > kfree(fid->rdir); > kfree(fid); > } > diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c > index bf459ee..94ef685 100644 > --- a/net/9p/trans_fd.c > +++ b/net/9p/trans_fd.c > @@ -197,15 +197,14 @@ static void p9_mux_poll_stop(struct p9_conn *m) > static void p9_conn_cancel(struct p9_conn *m, int err) > { > struct p9_req_t *req, *rtmp; > - unsigned long flags; > LIST_HEAD(cancel_list); > > p9_debug(P9_DEBUG_ERROR, "mux %p err %d\n", m, err); > > - spin_lock_irqsave(&m->client->lock, flags); > + spin_lock(&m->client->lock); > > if (m->err) { > - spin_unlock_irqrestore(&m->client->lock, flags); > + spin_unlock(&m->client->lock); > return; > } > > @@ -217,7 +216,7 @@ static void p9_conn_cancel(struct p9_conn *m, int err) > list_for_each_entry_safe(req, rtmp, &m->unsent_req_list, req_list) { > list_move(&req->req_list, &cancel_list); > } > - spin_unlock_irqrestore(&m->client->lock, flags); > + spin_unlock(&m->client->lock); > > list_for_each_entry_safe(req, rtmp, &cancel_list, req_list) { > p9_debug(P9_DEBUG_ERROR, "call back req %p\n", req); > --
-- Dominique Martinet
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