| Message ID | 20240206125145.354557-1-jiri@resnulli.us (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net] dpll: fix possible deadlock during netlink dump operation | expand |
On 06/02/2024 12:51, Jiri Pirko wrote: > From: Jiri Pirko <jiri@nvidia.com> > > Recently, I've been hitting following deadlock warning during dpll pin > dump: > > [52804.637962] ====================================================== > [52804.638536] WARNING: possible circular locking dependency detected > [52804.639111] 6.8.0-rc2jiri+ #1 Not tainted > [52804.639529] ------------------------------------------------------ > [52804.640104] python3/2984 is trying to acquire lock: > [52804.640581] ffff88810e642678 (nlk_cb_mutex-GENERIC){+.+.}-{3:3}, at: netlink_dump+0xb3/0x780 > [52804.641417] > but task is already holding lock: > [52804.642010] ffffffff83bde4c8 (dpll_lock){+.+.}-{3:3}, at: dpll_lock_dumpit+0x13/0x20 > [52804.642747] > which lock already depends on the new lock. > > [52804.643551] > the existing dependency chain (in reverse order) is: > [52804.644259] > -> #1 (dpll_lock){+.+.}-{3:3}: > [52804.644836] lock_acquire+0x174/0x3e0 > [52804.645271] __mutex_lock+0x119/0x1150 > [52804.645723] dpll_lock_dumpit+0x13/0x20 > [52804.646169] genl_start+0x266/0x320 > [52804.646578] __netlink_dump_start+0x321/0x450 > [52804.647056] genl_family_rcv_msg_dumpit+0x155/0x1e0 > [52804.647575] genl_rcv_msg+0x1ed/0x3b0 > [52804.648001] netlink_rcv_skb+0xdc/0x210 > [52804.648440] genl_rcv+0x24/0x40 > [52804.648831] netlink_unicast+0x2f1/0x490 > [52804.649290] netlink_sendmsg+0x36d/0x660 > [52804.649742] __sock_sendmsg+0x73/0xc0 > [52804.650165] __sys_sendto+0x184/0x210 > [52804.650597] __x64_sys_sendto+0x72/0x80 > [52804.651045] do_syscall_64+0x6f/0x140 > [52804.651474] entry_SYSCALL_64_after_hwframe+0x46/0x4e > [52804.652001] > -> #0 (nlk_cb_mutex-GENERIC){+.+.}-{3:3}: > [52804.652650] check_prev_add+0x1ae/0x1280 > [52804.653107] __lock_acquire+0x1ed3/0x29a0 > [52804.653559] lock_acquire+0x174/0x3e0 > [52804.653984] __mutex_lock+0x119/0x1150 > [52804.654423] netlink_dump+0xb3/0x780 > [52804.654845] __netlink_dump_start+0x389/0x450 > [52804.655321] genl_family_rcv_msg_dumpit+0x155/0x1e0 > [52804.655842] genl_rcv_msg+0x1ed/0x3b0 > [52804.656272] netlink_rcv_skb+0xdc/0x210 > [52804.656721] genl_rcv+0x24/0x40 > [52804.657119] netlink_unicast+0x2f1/0x490 > [52804.657570] netlink_sendmsg+0x36d/0x660 > [52804.658022] __sock_sendmsg+0x73/0xc0 > [52804.658450] __sys_sendto+0x184/0x210 > [52804.658877] __x64_sys_sendto+0x72/0x80 > [52804.659322] do_syscall_64+0x6f/0x140 > [52804.659752] entry_SYSCALL_64_after_hwframe+0x46/0x4e > [52804.660281] > other info that might help us debug this: > > [52804.661077] Possible unsafe locking scenario: > > [52804.661671] CPU0 CPU1 > [52804.662129] ---- ---- > [52804.662577] lock(dpll_lock); > [52804.662924] lock(nlk_cb_mutex-GENERIC); > [52804.663538] lock(dpll_lock); > [52804.664073] lock(nlk_cb_mutex-GENERIC); > [52804.664490] > > The issue as follows: __netlink_dump_start() calls control->start(cb) > with nlk->cb_mutex held. In control->start(cb) the dpll_lock is taken. > Then nlk->cb_mutex is released and taken again in netlink_dump(), while > dpll_lock still being held. That leads to ABBA deadlock when another > CPU races with the same operation. > > Fix this by moving dpll_lock taking into dumpit() callback which ensures > correct lock taking order. > > Fixes: 9d71b54b65b1 ("dpll: netlink: Add DPLL framework base functions") > Signed-off-by: Jiri Pirko <jiri@nvidia.com> Good catch, thanks! Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev> > --- > drivers/dpll/dpll_netlink.c | 20 ++++++-------------- > drivers/dpll/dpll_nl.c | 4 ---- > 2 files changed, 6 insertions(+), 18 deletions(-) > > diff --git a/drivers/dpll/dpll_netlink.c b/drivers/dpll/dpll_netlink.c > index 314bb3775465..4ca9ad16cd95 100644 > --- a/drivers/dpll/dpll_netlink.c > +++ b/drivers/dpll/dpll_netlink.c > @@ -1199,6 +1199,7 @@ int dpll_nl_pin_get_dumpit(struct sk_buff *skb, struct netlink_callback *cb) > unsigned long i; > int ret = 0; > > + mutex_lock(&dpll_lock); > xa_for_each_marked_start(&dpll_pin_xa, i, pin, DPLL_REGISTERED, > ctx->idx) { > if (!dpll_pin_available(pin)) > @@ -1218,6 +1219,8 @@ int dpll_nl_pin_get_dumpit(struct sk_buff *skb, struct netlink_callback *cb) > } > genlmsg_end(skb, hdr); > } > + mutex_unlock(&dpll_lock); > + > if (ret == -EMSGSIZE) { > ctx->idx = i; > return skb->len; > @@ -1373,6 +1376,7 @@ int dpll_nl_device_get_dumpit(struct sk_buff *skb, struct netlink_callback *cb) > unsigned long i; > int ret = 0; > > + mutex_lock(&dpll_lock); > xa_for_each_marked_start(&dpll_device_xa, i, dpll, DPLL_REGISTERED, > ctx->idx) { > hdr = genlmsg_put(skb, NETLINK_CB(cb->skb).portid, > @@ -1389,6 +1393,8 @@ int dpll_nl_device_get_dumpit(struct sk_buff *skb, struct netlink_callback *cb) > } > genlmsg_end(skb, hdr); > } > + mutex_unlock(&dpll_lock); > + > if (ret == -EMSGSIZE) { > ctx->idx = i; > return skb->len; > @@ -1439,20 +1445,6 @@ dpll_unlock_doit(const struct genl_split_ops *ops, struct sk_buff *skb, > mutex_unlock(&dpll_lock); > } > > -int dpll_lock_dumpit(struct netlink_callback *cb) > -{ > - mutex_lock(&dpll_lock); > - > - return 0; > -} > - > -int dpll_unlock_dumpit(struct netlink_callback *cb) > -{ > - mutex_unlock(&dpll_lock); > - > - return 0; > -} > - > int dpll_pin_pre_doit(const struct genl_split_ops *ops, struct sk_buff *skb, > struct genl_info *info) > { > diff --git a/drivers/dpll/dpll_nl.c b/drivers/dpll/dpll_nl.c > index eaee5be7aa64..1e95f5397cfc 100644 > --- a/drivers/dpll/dpll_nl.c > +++ b/drivers/dpll/dpll_nl.c > @@ -95,9 +95,7 @@ static const struct genl_split_ops dpll_nl_ops[] = { > }, > { > .cmd = DPLL_CMD_DEVICE_GET, > - .start = dpll_lock_dumpit, > .dumpit = dpll_nl_device_get_dumpit, > - .done = dpll_unlock_dumpit, > .flags = GENL_ADMIN_PERM | GENL_CMD_CAP_DUMP, > }, > { > @@ -129,9 +127,7 @@ static const struct genl_split_ops dpll_nl_ops[] = { > }, > { > .cmd = DPLL_CMD_PIN_GET, > - .start = dpll_lock_dumpit, > .dumpit = dpll_nl_pin_get_dumpit, > - .done = dpll_unlock_dumpit, > .policy = dpll_pin_get_dump_nl_policy, > .maxattr = DPLL_A_PIN_ID, > .flags = GENL_ADMIN_PERM | GENL_CMD_CAP_DUMP,
On Tue, 6 Feb 2024 13:51:45 +0100 Jiri Pirko wrote:
> drivers/dpll/dpll_nl.c | 4 ----
// SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)
/* Do not edit directly, auto-generated from: */
/* Documentation/netlink/specs/dpll.yaml */
/* YNL-GEN kernel source */
Wed, Feb 07, 2024 at 04:07:30AM CET, kuba@kernel.org wrote: >On Tue, 6 Feb 2024 13:51:45 +0100 Jiri Pirko wrote: >> drivers/dpll/dpll_nl.c | 4 ---- > >// SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) >/* Do not edit directly, auto-generated from: */ >/* Documentation/netlink/specs/dpll.yaml */ >/* YNL-GEN kernel source */ Doh! >-- >pw-bot: cr
diff --git a/drivers/dpll/dpll_netlink.c b/drivers/dpll/dpll_netlink.c index 314bb3775465..4ca9ad16cd95 100644 --- a/drivers/dpll/dpll_netlink.c +++ b/drivers/dpll/dpll_netlink.c @@ -1199,6 +1199,7 @@ int dpll_nl_pin_get_dumpit(struct sk_buff *skb, struct netlink_callback *cb) unsigned long i; int ret = 0; + mutex_lock(&dpll_lock); xa_for_each_marked_start(&dpll_pin_xa, i, pin, DPLL_REGISTERED, ctx->idx) { if (!dpll_pin_available(pin)) @@ -1218,6 +1219,8 @@ int dpll_nl_pin_get_dumpit(struct sk_buff *skb, struct netlink_callback *cb) } genlmsg_end(skb, hdr); } + mutex_unlock(&dpll_lock); + if (ret == -EMSGSIZE) { ctx->idx = i; return skb->len; @@ -1373,6 +1376,7 @@ int dpll_nl_device_get_dumpit(struct sk_buff *skb, struct netlink_callback *cb) unsigned long i; int ret = 0; + mutex_lock(&dpll_lock); xa_for_each_marked_start(&dpll_device_xa, i, dpll, DPLL_REGISTERED, ctx->idx) { hdr = genlmsg_put(skb, NETLINK_CB(cb->skb).portid, @@ -1389,6 +1393,8 @@ int dpll_nl_device_get_dumpit(struct sk_buff *skb, struct netlink_callback *cb) } genlmsg_end(skb, hdr); } + mutex_unlock(&dpll_lock); + if (ret == -EMSGSIZE) { ctx->idx = i; return skb->len; @@ -1439,20 +1445,6 @@ dpll_unlock_doit(const struct genl_split_ops *ops, struct sk_buff *skb, mutex_unlock(&dpll_lock); } -int dpll_lock_dumpit(struct netlink_callback *cb) -{ - mutex_lock(&dpll_lock); - - return 0; -} - -int dpll_unlock_dumpit(struct netlink_callback *cb) -{ - mutex_unlock(&dpll_lock); - - return 0; -} - int dpll_pin_pre_doit(const struct genl_split_ops *ops, struct sk_buff *skb, struct genl_info *info) { diff --git a/drivers/dpll/dpll_nl.c b/drivers/dpll/dpll_nl.c index eaee5be7aa64..1e95f5397cfc 100644 --- a/drivers/dpll/dpll_nl.c +++ b/drivers/dpll/dpll_nl.c @@ -95,9 +95,7 @@ static const struct genl_split_ops dpll_nl_ops[] = { }, { .cmd = DPLL_CMD_DEVICE_GET, - .start = dpll_lock_dumpit, .dumpit = dpll_nl_device_get_dumpit, - .done = dpll_unlock_dumpit, .flags = GENL_ADMIN_PERM | GENL_CMD_CAP_DUMP, }, { @@ -129,9 +127,7 @@ static const struct genl_split_ops dpll_nl_ops[] = { }, { .cmd = DPLL_CMD_PIN_GET, - .start = dpll_lock_dumpit, .dumpit = dpll_nl_pin_get_dumpit, - .done = dpll_unlock_dumpit, .policy = dpll_pin_get_dump_nl_policy, .maxattr = DPLL_A_PIN_ID, .flags = GENL_ADMIN_PERM | GENL_CMD_CAP_DUMP,