[RFC net-next 1/2] net/smc: refactoring lgr pending lock

D. Wythe
2023-09-06T13:55:46Z

From: "D. Wythe" <alibuda@linux.alibaba.com>

This patch replaces the locking and unlocking of lgr pending with
a unified inline function, and since the granularity of lgr pending
lock is within the lifecycle of init_info, which make it possible
to record the lock state on init_info. So that other routines can
unlock lgr pending lock safely.

Signed-off-by: D. Wythe <alibuda@linux.alibaba.com>
---
net/smc/af_smc.c | 24 ++++++++++++------------
net/smc/smc_core.h | 21 +++++++++++++++++++++
2 files changed, 33 insertions(+), 12 deletions(-)

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index bacdd97..52a987b 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -1251,10 +1251,10 @@ static int smc_connect_rdma(struct smc_sock *smc,
if (reason_code)
return reason_code;

- mutex_lock(&smc_client_lgr_pending);
+ smc_lgr_pending_lock(ini, &smc_client_lgr_pending);
reason_code = smc_conn_create(smc, ini);
if (reason_code) {
- mutex_unlock(&smc_client_lgr_pending);
+ smc_lgr_pending_unlock(ini, &smc_client_lgr_pending);
return reason_code;
}

@@ -1346,7 +1346,7 @@ static int smc_connect_rdma(struct smc_sock *smc,
if (reason_code)
goto connect_abort;
}
- mutex_unlock(&smc_client_lgr_pending);
+ smc_lgr_pending_unlock(ini, &smc_client_lgr_pending);

smc_copy_sock_settings_to_clc(smc);
smc->connect_nonblock = 0;
@@ -1356,7 +1356,7 @@ static int smc_connect_rdma(struct smc_sock *smc,
return 0;
connect_abort:
smc_conn_abort(smc, ini->first_contact_local);
- mutex_unlock(&smc_client_lgr_pending);
+ smc_lgr_pending_unlock(ini, &smc_client_lgr_pending);
smc->connect_nonblock = 0;

return reason_code;
@@ -1413,10 +1413,10 @@ static int smc_connect_ism(struct smc_sock *smc,
ini->ism_peer_gid[ini->ism_selected] = aclc->d0.gid;

/* there is only one lgr role for SMC-D; use server lock */
- mutex_lock(&smc_server_lgr_pending);
+ smc_lgr_pending_lock(ini, &smc_server_lgr_pending);
rc = smc_conn_create(smc, ini);
if (rc) {
- mutex_unlock(&smc_server_lgr_pending);
+ smc_lgr_pending_unlock(ini, &smc_server_lgr_pending);
return rc;
}

@@ -1443,7 +1443,7 @@ static int smc_connect_ism(struct smc_sock *smc,
aclc->hdr.version, eid, ini);
if (rc)
goto connect_abort;
- mutex_unlock(&smc_server_lgr_pending);
+ smc_lgr_pending_unlock(ini, &smc_server_lgr_pending);

smc_copy_sock_settings_to_clc(smc);
smc->connect_nonblock = 0;
@@ -1453,7 +1453,7 @@ static int smc_connect_ism(struct smc_sock *smc,
return 0;
connect_abort:
smc_conn_abort(smc, ini->first_contact_local);
- mutex_unlock(&smc_server_lgr_pending);
+ smc_lgr_pending_unlock(ini, &smc_server_lgr_pending);
smc->connect_nonblock = 0;

return rc;
@@ -2460,7 +2460,7 @@ static void smc_listen_work(struct work_struct *work)
if (rc)
goto out_decl;

- mutex_lock(&smc_server_lgr_pending);
+ smc_lgr_pending_lock(ini, &smc_server_lgr_pending);
smc_close_init(new_smc);
smc_rx_init(new_smc);
smc_tx_init(new_smc);
@@ -2479,7 +2479,7 @@ static void smc_listen_work(struct work_struct *work)

/* SMC-D does not need this lock any more */
if (ini->is_smcd)
- mutex_unlock(&smc_server_lgr_pending);
+ smc_lgr_pending_unlock(ini, &smc_server_lgr_pending);

/* receive SMC Confirm CLC message */
memset(buf, 0, sizeof(*buf));
@@ -2510,7 +2510,7 @@ static void smc_listen_work(struct work_struct *work)
ini->first_contact_local, ini);
if (rc)
goto out_unlock;
- mutex_unlock(&smc_server_lgr_pending);
+ smc_lgr_pending_unlock(ini, &smc_server_lgr_pending);
}
smc_conn_save_peer_info(new_smc, cclc);
smc_listen_out_connected(new_smc);
@@ -2518,7 +2518,7 @@ static void smc_listen_work(struct work_struct *work)
goto out_free;

out_unlock:
- mutex_unlock(&smc_server_lgr_pending);
+ smc_lgr_pending_unlock(ini, &smc_server_lgr_pending);
out_decl:
smc_listen_decline(new_smc, rc, ini ? ini->first_contact_local : 0,
proposal_version);
diff --git a/net/smc/smc_core.h b/net/smc/smc_core.h
index 120027d..6f309a3 100644
--- a/net/smc/smc_core.h
+++ b/net/smc/smc_core.h
@@ -422,6 +422,8 @@ struct smc_init_info {
u8 ism_offered_cnt; /* # of ISM devices offered */
u8 ism_selected; /* index of selected ISM dev*/
u8 smcd_version;
+ /* mutex holding for conn create */
+ struct mutex *mutex;
};

/* Find the connection associated with the given alert token in the link group.
@@ -589,6 +591,25 @@ struct smc_link *smc_switch_conns(struct smc_link_group *lgr,
int smcr_nl_get_link(struct sk_buff *skb, struct netlink_callback *cb);
int smcd_nl_get_lgr(struct sk_buff *skb, struct netlink_callback *cb);

+static inline void smc_lgr_pending_lock(struct smc_init_info *ini, struct mutex *lock)
+{
+ if (unlikely(ini->mutex))
+ pr_warn_once("smc: lgr pending deadlock dected.");
+
+ mutex_lock(lock);
+ ini->mutex = lock;
+}
+
+static inline void smc_lgr_pending_unlock(struct smc_init_info *ini, struct mutex *lock)
+{
+ /* already unlock it */
+ if (!ini->mutex)
+ return;
+
+ ini->mutex = NULL;
+ mutex_unlock(lock);
+}
+
static inline struct smc_link_group *smc_get_lgr(struct smc_link *link)
{
return link->lgr;
--
1.8.3.1