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Generation numbers to catch write back of stale copies

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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.
This commit is contained in:
Markus Armbruster 2009-03-01 18:56:41 +01:00
parent f8be963202
commit 20b31defe7
19 changed files with 82 additions and 3 deletions
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2
include/nat.h
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@ -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 */