Generation numbers to catch write back of stale copies

Oops when a stale copy is written back, i.e. the processor was yielded
since the copy was made.  Such bugs are difficult to spot.  Sequence
numbers catch them when they do actual harm (they also catch different
bugs).  Generation numbers catch them even when they don't.

New ef_generation to count generations.  Call new ef_make_stale() to
step it whenever the processor may be yielded.

New struct emptypedstr member generation.  Make sure all members of
unit empobj_storage share it.  It is only used in copies; its value on
disk and in the cache is meaningless.  Set it to ef_generation by
calling new ef_mark_fresh() when making copies in ef_read() and
ef_blank().  Do the same in obj_changed() to make check_sect_ok() &
friends freshen their argument when it is unchanged.  Copies with
generation other than ef_generation are stale.

Oops in ef_write() when a stale copy is written back.

diff --git a/include/commodity.h b/include/commodity.h
index e35457851aaee7515c5f13a044176e03767af396..38ef099069b7bf37682af19cdcefef78745a0652 100644 (file)
--- a/include/commodity.h
+++ b/include/commodity.h
@@ -45,6 +45,7 @@ struct comstr {
     short ef_type;
     short com_uid;
     unsigned com_seqno;
+    unsigned com_generation;
     time_t com_timestamp;
     natid com_owner;
     /* end of part matching struct empobj */

diff --git a/include/empobj.h b/include/empobj.h
index 713f2f4a50e118773e748c849faaf291d8bd9200..3906c13a639d280f3cb3185b737057b7aa065a77 100644 (file)
--- a/include/empobj.h
+++ b/include/empobj.h
@@ -58,6 +58,7 @@ struct empobj {
     short ef_type;
     short uid;
     unsigned seqno;
+    unsigned generation;
     time_t timestamp;
     /* end of part matching struct emptypedstr */
     natid own;         /* valid if EFF_OWNER is in table's flags */

diff --git a/include/file.h b/include/file.h
index 9aa6f38920565c961bb9dde952538e53040e668c..0ffa5b0cf450563aa00f2fdbac432f752d838d22 100644 (file)
--- a/include/file.h
+++ b/include/file.h
@@ -88,6 +88,7 @@ struct emptypedstr {
     short ef_type;
     short uid;
     unsigned seqno;
+    unsigned generation;
     time_t timestamp;
 };
 
@@ -203,6 +204,8 @@ enum {
 
 extern struct castr *ef_cadef(int);
 extern int ef_read(int, int, void *);
+extern void ef_make_stale(void);
+extern void ef_mark_fresh(int, void *);
 extern void *ef_ptr(int, int);
 extern char *ef_nameof(int);
 extern time_t ef_mtime(int);

diff --git a/include/game.h b/include/game.h
index 9f77dc0ff875a3cdbb14153c9de917151ed96928..b10426fc5de952caf6b81319edcb0c590caaf4e1 100644 (file)
--- a/include/game.h
+++ b/include/game.h
@@ -41,6 +41,7 @@ struct gamestr {
     short ef_type;
     short game_uid;
     unsigned game_seqno;
+    unsigned game_generation;
     time_t game_timestamp;
     /* end of part matching struct empobj */
     char game_upd_disable;     /* updates disabled? */

diff --git a/include/land.h b/include/land.h
index 6f5232ffc12cef5fdbaf17a1412809ef14b725a4..99f9c301faf04c2ce96b9a03888f766ee44fbabb 100644 (file)
--- a/include/land.h
+++ b/include/land.h
@@ -52,6 +52,7 @@ struct lndstr {
     short ef_type;
     short lnd_uid;             /* unit id (land unit) */
     unsigned lnd_seqno;
+    unsigned lnd_generation;
     time_t lnd_timestamp;      /* Last time this unit was touched */
     natid lnd_own;             /* owner's country num */
     coord lnd_x;               /* x location in abs coords */

diff --git a/include/loan.h b/include/loan.h
index f4f900f7c80b1dd28ef263448b77cc3713a3fe9d..fbfe1568760e765da799985e12a360fd016bf437 100644 (file)
--- a/include/loan.h
+++ b/include/loan.h
@@ -45,6 +45,7 @@ struct lonstr {
     short ef_type;
     short l_uid;
     unsigned l_seqno;
+    unsigned l_generation;
     time_t l_timestamp;
     /* end of part matching struct empobj */
     natid l_loner;             /* loan shark */

diff --git a/include/lost.h b/include/lost.h
index d30f8e856b0399308b81ad06f081dbaf4adc2fae..021f26338910f901a16297280a9a9460b8245288 100644 (file)
--- a/include/lost.h
+++ b/include/lost.h
@@ -42,6 +42,7 @@ struct loststr {
     short ef_type;
     short lost_uid;
     unsigned lost_seqno;
+    unsigned lost_generation;
     time_t lost_timestamp;     /* When it was lost */
     natid lost_owner;          /* Who lost it */
     /* end of part matching struct empobj */

diff --git a/include/nat.h b/include/nat.h
index 5749a1bd0bdbafd7042651fd718ed138bb0387b6..e4c135f93d39d9a3d0ff428a42f6e5aa208c9283 100644 (file)
--- a/include/nat.h
+++ b/include/nat.h
@@ -73,6 +73,7 @@ struct realmstr {
     short ef_type;
     short r_uid;               /* realm table index */
     unsigned r_seqno;
+    unsigned r_generation;
     time_t r_timestamp;                /* Last time this realm was touched */
     natid r_cnum;              /* country number */
     /* end of part matching struct empobj */
@@ -86,6 +87,7 @@ struct natstr {
     short ef_type;
     short nat_uid;             /* equals nat_cnum */
     unsigned nat_seqno;
+    unsigned nat_generation;
     time_t nat_timestamp;
     natid nat_cnum;            /* our country number */
     /* end of part matching struct empobj */

diff --git a/include/news.h b/include/news.h
index 24554f096c32da24e3fa7b93404e994d21c10993..01a47826b3f4ae03a40816e47800cacd210c4e9b 100644 (file)
--- a/include/news.h
+++ b/include/news.h
@@ -49,6 +49,7 @@ struct nwsstr {
     short ef_type;
     short nws_uid;
     unsigned nws_seqno;
+    unsigned nws_generation;
     time_t nws_timestamp;
     /* end of part matching struct empobj */
     natid nws_ano;             /* "actor" country # */

diff --git a/include/nuke.h b/include/nuke.h
index 231f0a04578982578a87e3b9483e9c2e4d4436b3..bb1efd53349ffe6afed7e3d2ca20b59d1a04d734 100644 (file)
--- a/include/nuke.h
+++ b/include/nuke.h
@@ -45,6 +45,7 @@ struct nukstr {
     short ef_type;
     short nuk_uid;
     unsigned nuk_seqno;
+    unsigned nuk_generation;
     time_t nuk_timestamp;      /* Last time this nuke was touched */
     natid nuk_own;
     coord nuk_x, nuk_y;                /* current loc of device */

diff --git a/include/plane.h b/include/plane.h
index 8e37d0d2b784840ee25c3672b0127ccc4d1c35b1..5e809e2dff03d57c605ad9480af3881146479d8f 100644 (file)
--- a/include/plane.h
+++ b/include/plane.h
@@ -49,6 +49,7 @@ struct plnstr {
     short ef_type;
     short pln_uid;             /* plane unit id */
     unsigned pln_seqno;
+    unsigned pln_generation;
     time_t pln_timestamp;      /* Last time this plane was touched */
     natid pln_own;             /* owning country */
     coord pln_x;               /* plane x-y */

diff --git a/include/sect.h b/include/sect.h
index 336b71f11930e9521c275f06ebfb6ccc45455782..f242b22f668e392a9d5c2b844c67ff3f321d01b1 100644 (file)
--- a/include/sect.h
+++ b/include/sect.h
@@ -47,6 +47,7 @@ struct sctstr {
     short ef_type;
     short sct_uid;             /* equals XYOFFSET(sct_x, sct_y) */
     unsigned sct_seqno;
+    unsigned sct_generation;
     time_t sct_timestamp;      /* Last time this sector was written to */
     natid sct_own;             /* owner's country num */
     coord sct_x;               /* x coord of sector */

diff --git a/include/ship.h b/include/ship.h
index 21e749f589412605affa408e24d725b7075aaa9b..a8762d5783ffcd20b72a0916494c991d260c030d 100644 (file)
--- a/include/ship.h
+++ b/include/ship.h
@@ -66,6 +66,7 @@ struct shpstr {
     short ef_type;
     short shp_uid;             /* unit id (ship #) */
     unsigned shp_seqno;
+    unsigned shp_generation;
     time_t shp_timestamp;      /* Last time this ship was touched. */
     natid shp_own;             /* owner's country num */
     coord shp_x;               /* x location in abs coords */

diff --git a/include/trade.h b/include/trade.h
index 6fc9919e274414e7aa20695cf7f73bce8582ad71..26449ae841f072b1c5ffee43ad6853ffd168aa5b 100644 (file)
--- a/include/trade.h
+++ b/include/trade.h
@@ -45,6 +45,7 @@ struct trdstr {
     short ef_type;
     short trd_uid;
     unsigned trd_seqno;
+    unsigned trd_generation;
     time_t trd_timestamp;
     natid trd_owner;
     /* end of part matching struct empobj */

diff --git a/include/treaty.h b/include/treaty.h
index 0e164eef5df1fb8fc2bcf31b7c97e7e0e15b91e5..e70c2f98678b49730bc6ab78a3e01a02e713bcdf 100644 (file)
--- a/include/treaty.h
+++ b/include/treaty.h
@@ -42,6 +42,7 @@ struct trtstr {
     short ef_type;
     short trt_uid;
     unsigned trt_seqno;
+    unsigned trt_generation;
     time_t trt_timestamp;
     /* end of part matching struct empobj */
     natid trt_cna;             /* proposer */

diff --git a/src/lib/common/file.c b/src/lib/common/file.c
index 908b024b7051e0cea7ce1871a4e35f5889ef8bbf..16633eee94d01963869f715800399b305800ed49 100644 (file)
--- a/src/lib/common/file.c
+++ b/src/lib/common/file.c
@@ -52,9 +52,12 @@ static int do_read(struct empfile *, void *, int, int);
 static int do_write(struct empfile *, void *, int, int);
 static unsigned get_seqno(struct empfile *, int);
 static void new_seqno(struct empfile *, void *);
+static void must_be_fresh(struct empfile *, void *);
 static void do_blank(struct empfile *, void *, int, int);
 static int ef_check(int);
 
+static unsigned ef_generation;
+
 /*
  * Open the file-backed table TYPE (EF_SECTOR, ...).
  * HOW are flags to control operation.  Naturally, immutable flags are
@@ -338,6 +341,7 @@ ef_read(int type, int id, void *into)
        cachep = ep->cache + (id - ep->baseid) * ep->size;
     }
     memcpy(into, cachep, ep->size);
+    ef_mark_fresh(type, into);
 
     if (ep->postread)
        ep->postread(id, into);
@@ -500,9 +504,11 @@ ef_write(int type, int id, void *from)
        if (ep->onresize && ep->onresize(type) < 0)
            return 0;
     }
-    if (id >= ep->baseid && id < ep->baseid + ep->cids)
+    if (id >= ep->baseid && id < ep->baseid + ep->cids) {
        cachep = ep->cache + (id - ep->baseid) * ep->size;
-    else
+       if (cachep != from)
+           must_be_fresh(ep, from);
+    } else
        cachep = NULL;
     if (ep->prewrite)
        ep->prewrite(id, cachep, from);
@@ -586,6 +592,35 @@ new_seqno(struct empfile *ep, void *buf)
     elt->seqno = old_seqno + 1;
 }
 
+void
+ef_make_stale(void)
+{
+    ef_generation++;
+}
+
+void
+ef_mark_fresh(int type, void *buf)
+{
+    struct empfile *ep;
+
+    if (ef_check(type) < 0)
+       return;
+    ep = &empfile[type];
+    if (!(ep->flags & EFF_TYPED))
+       return;
+    ((struct emptypedstr *)buf)->generation = ef_generation;
+}
+
+static void
+must_be_fresh(struct empfile *ep, void *buf)
+{
+    struct emptypedstr *elt = buf;
+
+    if (!(ep->flags & EFF_TYPED))
+       return;
+    CANT_HAPPEN(elt->generation != ef_generation);
+}
+
 /*
  * Extend table TYPE by COUNT elements.
  * Any pointers obtained from ef_ptr() become invalid.
@@ -663,6 +698,7 @@ ef_blank(int type, int id, void *buf)
        elt = buf;
        elt->seqno = get_seqno(ep, elt->uid);
     }
+    ef_mark_fresh(type, buf);
 }
 
 /*

diff --git a/src/lib/empthread/io.c b/src/lib/empthread/io.c
index 5bbce8d9761eeec09437520c7ad7ba63e40d3243..3fcf164bf96a026232d6e5d4a06cc070c1dfdd18 100644 (file)
--- a/src/lib/empthread/io.c
+++ b/src/lib/empthread/io.c
@@ -51,6 +51,7 @@
 #include <unistd.h>
 #include "empio.h"
 #include "empthread.h"
+#include "file.h"
 #include "ioqueue.h"
 #include "misc.h"
 #include "queue.h"
@@ -123,6 +124,9 @@ io_input(struct iop *iop, int waitforinput)
     int cc;
     int res;
 
+    if (waitforinput)
+       ef_make_stale();
+
     /* Not a read IOP */
     if ((iop->flags & IO_READ) == 0) {
        errno = EBADF;
@@ -183,6 +187,9 @@ io_output(struct iop *iop, int waitforoutput)
     int n;
     int remain;
 
+    if (waitforoutput)
+       ef_make_stale();
+
     /* If there is no output waiting. */
     if (!io_outputwaiting(iop))
        return 0;
@@ -264,6 +271,9 @@ io_write(struct iop *iop, char *buf, int nbytes, int doWait)
 {
     int len;
 
+    if (doWait)
+       ef_make_stale();
+
     if ((iop->flags & IO_WRITE) == 0)
        return -1;
     ioq_append(iop->output, buf, nbytes);
@@ -285,6 +295,8 @@ io_output_all(struct iop *iop)
 {
     int n;
 
+    ef_make_stale();
+
     /*
      * Mustn't block a player thread while update is pending, or else
      * a malicous player could delay the update indefinitely

diff --git a/src/lib/empthread/lwp.c b/src/lib/empthread/lwp.c
index 03bf4a64d18050cb8c427a8b6c5044f0a0f03c33..66015a78cbe635bf98551356fb250d5924d6e3bb 100644 (file)
--- a/src/lib/empthread/lwp.c
+++ b/src/lib/empthread/lwp.c
@@ -37,6 +37,7 @@
 #include <signal.h>
 #include <time.h>
 #include "empthread.h"
+#include "file.h"
 #include "misc.h"
 
 /* Flags that were passed to empth_init() */
@@ -65,6 +66,7 @@ empth_create(void (*entry)(void *), int size, int flags,
 {
     if (!flags)
        flags = empth_flags;
+    ef_make_stale();
     return lwpCreate(1, entry, size, flags, name, 0, 0, ud);
 }
 
@@ -89,18 +91,21 @@ empth_set_name(empth_t *thread, char *name)
 void
 empth_exit(void)
 {
+    ef_make_stale();
     lwpExit();
 }
 
 void
 empth_yield(void)
 {
+    ef_make_stale();
     lwpYield();
 }
 
 int
 empth_select(int fd, int flags, struct timeval *timeout)
 {
+    ef_make_stale();
     return lwpSleepFd(fd, flags, timeout);
 }
 
@@ -113,6 +118,7 @@ empth_wakeup(empth_t *a)
 int
 empth_sleep(time_t until)
 {
+    ef_make_stale();
     return lwpSleepUntil(until);
 }
 
@@ -123,6 +129,7 @@ empth_wait_for_signal(void)
     int sig, err;
     time_t now;
 
+    ef_make_stale();
     sigemptyset(&set);
     sigaddset(&set, SIGHUP);
     sigaddset(&set, SIGINT);
@@ -153,12 +160,14 @@ empth_rwlock_destroy(empth_rwlock_t *rwlock)
 void
 empth_rwlock_wrlock(empth_rwlock_t *rwlock)
 {
+    ef_make_stale();
     lwp_rwlock_wrlock(rwlock);
 }
 
 void
 empth_rwlock_rdlock(empth_rwlock_t *rwlock)
 {
+    ef_make_stale();
     lwp_rwlock_rdlock(rwlock);
 }
 

diff --git a/src/lib/subs/check.c b/src/lib/subs/check.c
index f20f961726f9adb10c8bebd06f7e4cf84e5e9392..6623a3ef5b16e9228b4884004f2c6f3ce56ad0ee 100644 (file)
--- a/src/lib/subs/check.c
+++ b/src/lib/subs/check.c
@@ -52,7 +52,11 @@ obj_changed(struct empobj *obj, size_t sz)
     get_empobj(obj->ef_type, obj->uid, &old);
     memcpy(&tobj, obj, sz);
     old.gen.timestamp = tobj.gen.timestamp = 0;
-    return memcmp(&tobj, &old, sz);
+    old.gen.generation = tobj.gen.generation = 0;
+    if (memcmp(&tobj, &old, sz))
+       return 1;
+    ef_mark_fresh(obj->ef_type, obj);
+    return 0;
 }
 
 int