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Clarify what wapbl_jlock_assert and wapbl_junlock_assert mean.

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riastradh 2015-04-01 22:51:33 +00:00
parent e4264474cf
commit 51820012f4
1 changed files with 36 additions and 4 deletions
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40
share/man/man9/wapbl.9
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@ -1,4 +1,4 @@
.\" $NetBSD: wapbl.9,v 1.9 2015/03/31 00:03:58 riastradh Exp $ .\" $NetBSD: wapbl.9,v 1.10 2015/04/01 22:51:33 riastradh Exp $
.\" .\"
.\" Copyright (c) 2015 The NetBSD Foundation, Inc. .\" Copyright (c) 2015 The NetBSD Foundation, Inc.
.\" All rights reserved. .\" All rights reserved.
@ -168,9 +168,9 @@ Either all writes issued between
and and
.Fn wapbl_end .Fn wapbl_end
will complete, or none of them will. will complete, or none of them will.
File systems can assert that the transaction should be locked with File systems can assert that the transaction is locked with
.Fn wapbl_jlock_assert , .Fn wapbl_jlock_assert ,
or unlocked, with or not exclusively locked, with
.Fn wapbl_junlock_assert . .Fn wapbl_junlock_assert .
.Pp .Pp
If a file system requires multiple transactions to initialize an If a file system requires multiple transactions to initialize an
@ -399,8 +399,33 @@ that was given to
.Fn wapbl_start . .Fn wapbl_start .
.It Fn wapbl_jlock_assert wl .It Fn wapbl_jlock_assert wl
Assert that the current transaction is locked. Assert that the current transaction is locked.
.Pp
Note that it might not be locked by the current thread: this assertion
passes if
.Em any
thread has it locked.
.It Fn wapbl_junlock_assert wl .It Fn wapbl_junlock_assert wl
Assert that the current transaction is unlocked. Assert that the current transaction is not exclusively locked by the
current thread.
.Pp
Users of
.Nm
observe exclusive locks only in the
.Fa flushfn
and
.Fa flushabortfn
callbacks to
.Fn wapbl_start .
Outside of such contexts, the transaction is never exclusively locked,
even between
.Fn wapbl_begin
and
.Fn wapbl_end .
.Pp
There is no way to assert that the current transaction is not locked at
all -- i.e., that the caller may lock the transaction with
.Fn wapbl_begin
without danger of deadlock.
.El .El
.Sh CODE REFERENCES .Sh CODE REFERENCES
The The
@ -465,6 +490,13 @@ occur in a single transaction -- there is no way to roll back the disk
block allocations if the write fails in the middle, e.g. because of a block allocations if the write fails in the middle, e.g. because of a
fault in the middle of the user buffer. fault in the middle of the user buffer.
.Pp .Pp
.Fn wapbl_jlock_assert
does not guarantee that the current thread has the current transaction
locked.
.Fn wapbl_junlock_assert
does not guarantee that the current thread does not have the current
transaction locked at all.
.Pp
There is only one There is only one
.Nm .Nm
transaction for each file system at any given time, and only one transaction for each file system at any given time, and only one