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Document 'socket' and 'sockbuf' structures locking
Guess it's time. `so_oobmark' marked as [mr]. It is accessed in
reception path and corresponding SS_RCVATMARK flag belongs `so_rcv'
buffer. However, it is still protected by exclusive solock()/netlock.
No functional changes.
Index: sys/sys/socketvar.h
===================================================================
RCS file: /cvs/src/sys/sys/socketvar.h,v
diff -u -p -r1.133 socketvar.h
--- sys/sys/socketvar.h 20 Jul 2024 17:26:19 -0000 1.133
+++ sys/sys/socketvar.h 24 Jul 2024 11:28:18 -0000
@@ -53,9 +53,11 @@ TAILQ_HEAD(soqhead, socket);
/*
* Locks used to protect global data and struct members:
+ * A atomic
* I immutable after creation
* mr sb_mxt of so_rcv buffer
* ms sb_mtx of so_snd buffer
+ * m sb_mtx
* br sblock() of so_rcv buffer
* bs sblock() od so_snd buffer
* s solock()
@@ -79,20 +81,56 @@ struct sosplice {
};
/*
+ * Variables for socket buffering.
+ */
+struct sockbuf {
+ struct rwlock sb_lock;
+ struct mutex sb_mtx;
+/* The following fields are all zeroed on flush. */
+#define sb_startzero sb_cc
+ u_long sb_cc; /* [m] actual chars in buffer */
+ u_long sb_datacc; /* [m] data only chars in buffer */
+ u_long sb_hiwat; /* [m] max actual char count */
+ u_long sb_wat; /* [m] default watermark */
+ u_long sb_mbcnt; /* [m] chars of mbufs used */
+ u_long sb_mbmax; /* [m] max chars of mbufs to use */
+ long sb_lowat; /* [m] low water mark */
+ struct mbuf *sb_mb; /* [m] the mbuf chain */
+ struct mbuf *sb_mbtail; /* [m] the last mbuf in the chain */
+ struct mbuf *sb_lastrecord; /* [m] first mbuf of last record in
+ socket buffer */
+ short sb_flags; /* [m] flags, see below */
+/* End area that is zeroed on flush. */
+#define sb_endzero sb_flags
+ short sb_state; /* [m] socket state on sockbuf */
+ uint64_t sb_timeo_nsecs; /* [m] timeout for read/write */
+ struct klist sb_klist; /* [m] list of knotes */
+};
+
+#define SB_MAX (2*1024*1024) /* default for max chars in sockbuf */
+#define SB_WAIT 0x0001 /* someone is waiting for data/space */
+#define SB_ASYNC 0x0002 /* ASYNC I/O, need signals */
+#define SB_SPLICE 0x0004 /* buffer is splice source or drain */
+#define SB_NOINTR 0x0008 /* operations not interruptible */
+#define SB_MTXLOCK 0x0010 /* sblock() doesn't need solock() */
+
+/*
* Kernel structure per socket.
* Contains send and receive buffer queues,
* handle on protocol and pointer to protocol
* private data and error information.
*/
struct socket {
- const struct protosw *so_proto; /* protocol handle */
+ const struct protosw *so_proto; /* [I] protocol handle */
struct rwlock so_lock; /* this socket lock */
struct refcnt so_refcnt; /* references to this socket */
- void *so_pcb; /* protocol control block */
- u_int so_state; /* internal state flags SS_*, below */
- short so_type; /* generic type, see socket.h */
- short so_options; /* from socket call, see socket.h */
- short so_linger; /* time to linger while closing */
+ void *so_pcb; /* [s] protocol control block */
+ u_int so_state; /* [s] internal state flags SS_*,
+ see below */
+ short so_type; /* [I] generic type, see socket.h */
+ short so_options; /* [s] from socket call, see
+ socket.h */
+ short so_linger; /* [s] time to linger while closing */
/*
* Variables for connection queueing.
* Socket where accepts occur is so_head in all subsidiary sockets.
@@ -103,59 +141,37 @@ struct socket {
* it has to be pulled out of either so_q0 or so_q.
* We allow connections to queue up based on current queue lengths
* and limit on number of queued connections for this socket.
- */
- struct socket *so_head; /* back pointer to accept socket */
- struct soqhead *so_onq; /* queue (q or q0) that we're on */
- struct soqhead so_q0; /* queue of partial connections */
- struct soqhead so_q; /* queue of incoming connections */
+ *
+ * Connections queue relies on both socket locks of listening and
+ * unaccepted sockets. Socket lock of listening socket should be
+ * always taken first.
+ */
+ struct socket *so_head; /* [s] back pointer to accept socket */
+ struct soqhead *so_onq; /* [s] queue (q or q0) that we're on */
+ struct soqhead so_q0; /* [s] queue of partial connections */
+ struct soqhead so_q; /* [s] queue of incoming connections */
struct sigio_ref so_sigio; /* async I/O registration */
- TAILQ_ENTRY(socket) so_qe; /* our queue entry (q or q0) */
- short so_q0len; /* partials on so_q0 */
- short so_qlen; /* number of connections on so_q */
- short so_qlimit; /* max number queued connections */
- short so_timeo; /* connection timeout */
- u_long so_oobmark; /* chars to oob mark */
- u_int so_error; /* error affecting connection */
+ TAILQ_ENTRY(socket) so_qe; /* [s] our queue entry (q or q0) */
+ short so_q0len; /* [s] partials on so_q0 */
+ short so_qlen; /* [s] number of connections on so_q */
+ short so_qlimit; /* [s] max number queued connections */
+ short so_timeo; /* [s] connection timeout */
+ u_long so_oobmark; /* [mr] chars to oob mark */
+ u_int so_error; /* [A] error affecting connection */
struct sosplice *so_sp; /* [s br] */
-/*
- * Variables for socket buffering.
- */
- struct sockbuf {
- struct rwlock sb_lock;
- struct mutex sb_mtx;
-/* The following fields are all zeroed on flush. */
-#define sb_startzero sb_cc
- u_long sb_cc; /* actual chars in buffer */
- u_long sb_datacc; /* data only chars in buffer */
- u_long sb_hiwat; /* max actual char count */
- u_long sb_wat; /* default watermark */
- u_long sb_mbcnt; /* chars of mbufs used */
- u_long sb_mbmax; /* max chars of mbufs to use */
- long sb_lowat; /* low water mark */
- struct mbuf *sb_mb; /* the mbuf chain */
- struct mbuf *sb_mbtail; /* the last mbuf in the chain */
- struct mbuf *sb_lastrecord;/* first mbuf of last record in
- socket buffer */
- short sb_flags; /* flags, see below */
-/* End area that is zeroed on flush. */
-#define sb_endzero sb_flags
- short sb_state; /* socket state on sockbuf */
- uint64_t sb_timeo_nsecs;/* timeout for read/write */
- struct klist sb_klist; /* process selecting read/write */
- } so_rcv, so_snd;
-#define SB_MAX (2*1024*1024) /* default for max chars in sockbuf */
-#define SB_WAIT 0x0001 /* someone is waiting for data/space */
-#define SB_ASYNC 0x0002 /* ASYNC I/O, need signals */
-#define SB_SPLICE 0x0004 /* buffer is splice source or drain */
-#define SB_NOINTR 0x0008 /* operations not interruptible */
-#define SB_MTXLOCK 0x0010 /* sblock() doesn't need solock() */
- void (*so_upcall)(struct socket *so, caddr_t arg, int waitf);
- caddr_t so_upcallarg; /* Arg for above */
- uid_t so_euid, so_ruid; /* who opened the socket */
- gid_t so_egid, so_rgid;
- pid_t so_cpid; /* pid of process that opened socket */
+ struct sockbuf so_rcv;
+ struct sockbuf so_snd;
+
+ void (*so_upcall)(struct socket *, caddr_t, int); /* [s] */
+ caddr_t so_upcallarg; /* [s] Arg for above */
+ uid_t so_euid; /* [I] who opened the socket */
+ uid_t so_ruid; /* [I] */
+ gid_t so_egid; /* [I] */
+ gid_t so_rgid; /* [I] */
+ pid_t so_cpid; /* [I] pid of process that opened
+ socket */
};
/*
Document 'socket' and 'sockbuf' structures locking