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Caution programmers not to confuse M_DONTWAIT with M_NOWAIT. They

are not the same.

Suggested by:	Hiten Pandya <hiten@unixdaemons.com>
This commit is contained in:
Robert Watson 2003-01-18 03:25:40 +00:00
parent da5e9a5bd6
commit eef9bd4c3f
Notes: svn2git 2020-12-20 02:59:44 +00:00
svn path=/head/; revision=109459
2 changed files with 19 additions and 0 deletions

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@ -159,6 +159,17 @@ is defined to be 0, meaning that blocking operation is the default.
Also note that
.Dv M_NOWAIT
is required when running in an interrupt context.
.Pp
Programmers should be careful not to confuse
.Dv M_NOWAIT ,
the
.Fn malloc
flag, with
.Dv M_DONTWAIT ,
an
.Xr mbuf 9
allocation flag, which is not a valid argument to
.Fn malloc .
.It Dv M_WAITOK
Indicates that it is Ok to wait for resources. It is unconveniently
defined as 0 so care should be taken never to compare against this value

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@ -295,6 +295,14 @@ number of ticks.
A number of other mbuf-related
functions and macros have the same argument because they may
at some point need to allocate new mbufs.
.Pp
Programmers should be careful not to confuse the mbuf allocation flag
.Dv M_DONTWAIT
with the
.Xr malloc 9
allocation flag,
.Dv M_NOWAIT .
They are not the same.
.It Fn MGETHDR mbuf how type
Allocate an mbuf and initialize it to contain a packet header
and internal data.