| Message ID | 825eb0c905cb864991eba335f4a2b780e543f06b.1677085641.git.lucien.xin@gmail.com (mailing list archive) |
|---|---|
| State | Accepted |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [PATCHv2,net] sctp: add a refcnt in sctp_stream_priorities to avoid a nested loop | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Clearly marked for net |
| netdev/fixes_present | success | Fixes tag present in non-next series |
| netdev/subject_prefix | success | Link |
| netdev/cover_letter | success | Single patches do not need cover letters |
| netdev/patch_count | success | Link |
| netdev/header_inline | success | No static functions without inline keyword in header files |
| netdev/build_32bit | success | Errors and warnings before: 46 this patch: 46 |
| netdev/cc_maintainers | success | CCed 10 of 10 maintainers |
| netdev/build_clang | success | Errors and warnings before: 0 this patch: 0 |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Signed-off-by tag matches author and committer |
| netdev/check_selftest | success | No net selftest shell script |
| netdev/verify_fixes | success | Fixes tag looks correct |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 46 this patch: 46 |
| netdev/checkpatch | warning | WARNING: line length of 96 exceeds 80 columns |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/source_inline | success | Was 0 now: 0 |
On Wed, 22 Feb 2023 12:07:21 -0500 Xin Long wrote: > With this refcnt added in sctp_stream_priorities, we don't need to > traverse all streams to check if the prio is used by other streams > when freeing one stream's prio in sctp_sched_prio_free_sid(). This > can avoid a nested loop (up to 65535 * 65535), which may cause a > stuck as Ying reported: > > watchdog: BUG: soft lockup - CPU#23 stuck for 26s! [ksoftirqd/23:136] > Call Trace: > <TASK> > sctp_sched_prio_free_sid+0xab/0x100 [sctp] > sctp_stream_free_ext+0x64/0xa0 [sctp] > sctp_stream_free+0x31/0x50 [sctp] > sctp_association_free+0xa5/0x200 [sctp] > > Note that it doesn't need to use refcount_t type for this counter, > as its accessing is always protected under the sock lock. > > v1->v2: > - add a check in sctp_sched_prio_set to avoid the possible prio_head > refcnt overflow. > > Fixes: 9ed7bfc79542 ("sctp: fix memory leak in sctp_stream_outq_migrate()") > Reported-by: Ying Xu <yinxu@redhat.com> > Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com> > Signed-off-by: Xin Long <lucien.xin@gmail.com> Applied, thanks!
diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h index afa3781e3ca2..e1f6e7fc2b11 100644 --- a/include/net/sctp/structs.h +++ b/include/net/sctp/structs.h @@ -1412,6 +1412,7 @@ struct sctp_stream_priorities { /* The next stream in line */ struct sctp_stream_out_ext *next; __u16 prio; + __u16 users; }; struct sctp_stream_out_ext { diff --git a/net/sctp/stream_sched_prio.c b/net/sctp/stream_sched_prio.c index 42d4800f263d..4d4d9da331f4 100644 --- a/net/sctp/stream_sched_prio.c +++ b/net/sctp/stream_sched_prio.c @@ -25,6 +25,18 @@ static void sctp_sched_prio_unsched_all(struct sctp_stream *stream); +static struct sctp_stream_priorities *sctp_sched_prio_head_get(struct sctp_stream_priorities *p) +{ + p->users++; + return p; +} + +static void sctp_sched_prio_head_put(struct sctp_stream_priorities *p) +{ + if (p && --p->users == 0) + kfree(p); +} + static struct sctp_stream_priorities *sctp_sched_prio_new_head( struct sctp_stream *stream, int prio, gfp_t gfp) { @@ -38,6 +50,7 @@ static struct sctp_stream_priorities *sctp_sched_prio_new_head( INIT_LIST_HEAD(&p->active); p->next = NULL; p->prio = prio; + p->users = 1; return p; } @@ -53,7 +66,7 @@ static struct sctp_stream_priorities *sctp_sched_prio_get_head( */ list_for_each_entry(p, &stream->prio_list, prio_sched) { if (p->prio == prio) - return p; + return sctp_sched_prio_head_get(p); if (p->prio > prio) break; } @@ -70,7 +83,7 @@ static struct sctp_stream_priorities *sctp_sched_prio_get_head( */ break; if (p->prio == prio) - return p; + return sctp_sched_prio_head_get(p); } /* If not even there, allocate a new one. */ @@ -154,32 +167,21 @@ static int sctp_sched_prio_set(struct sctp_stream *stream, __u16 sid, struct sctp_stream_out_ext *soute = sout->ext; struct sctp_stream_priorities *prio_head, *old; bool reschedule = false; - int i; + + old = soute->prio_head; + if (old && old->prio == prio) + return 0; prio_head = sctp_sched_prio_get_head(stream, prio, gfp); if (!prio_head) return -ENOMEM; reschedule = sctp_sched_prio_unsched(soute); - old = soute->prio_head; soute->prio_head = prio_head; if (reschedule) sctp_sched_prio_sched(stream, soute); - if (!old) - /* Happens when we set the priority for the first time */ - return 0; - - for (i = 0; i < stream->outcnt; i++) { - soute = SCTP_SO(stream, i)->ext; - if (soute && soute->prio_head == old) - /* It's still in use, nothing else to do here. */ - return 0; - } - - /* No hits, we are good to free it. */ - kfree(old); - + sctp_sched_prio_head_put(old); return 0; } @@ -206,20 +208,8 @@ static int sctp_sched_prio_init_sid(struct sctp_stream *stream, __u16 sid, static void sctp_sched_prio_free_sid(struct sctp_stream *stream, __u16 sid) { - struct sctp_stream_priorities *prio = SCTP_SO(stream, sid)->ext->prio_head; - int i; - - if (!prio) - return; - + sctp_sched_prio_head_put(SCTP_SO(stream, sid)->ext->prio_head); SCTP_SO(stream, sid)->ext->prio_head = NULL; - for (i = 0; i < stream->outcnt; i++) { - if (SCTP_SO(stream, i)->ext && - SCTP_SO(stream, i)->ext->prio_head == prio) - return; - } - - kfree(prio); } static void sctp_sched_prio_enqueue(struct sctp_outq *q,
With this refcnt added in sctp_stream_priorities, we don't need to traverse all streams to check if the prio is used by other streams when freeing one stream's prio in sctp_sched_prio_free_sid(). This can avoid a nested loop (up to 65535 * 65535), which may cause a stuck as Ying reported: watchdog: BUG: soft lockup - CPU#23 stuck for 26s! [ksoftirqd/23:136] Call Trace: <TASK> sctp_sched_prio_free_sid+0xab/0x100 [sctp] sctp_stream_free_ext+0x64/0xa0 [sctp] sctp_stream_free+0x31/0x50 [sctp] sctp_association_free+0xa5/0x200 [sctp] Note that it doesn't need to use refcount_t type for this counter, as its accessing is always protected under the sock lock. v1->v2: - add a check in sctp_sched_prio_set to avoid the possible prio_head refcnt overflow. Fixes: 9ed7bfc79542 ("sctp: fix memory leak in sctp_stream_outq_migrate()") Reported-by: Ying Xu <yinxu@redhat.com> Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com> Signed-off-by: Xin Long <lucien.xin@gmail.com> --- include/net/sctp/structs.h | 1 + net/sctp/stream_sched_prio.c | 52 +++++++++++++++--------------------- 2 files changed, 22 insertions(+), 31 deletions(-)