[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH XEN v8 14/29] tools/libs/foreignmemory: Mention restrictions on fork in docs.
On Tue, 2016-01-19 at 13:24 +0000, Wei Liu wrote: > On Fri, Jan 15, 2016 at 01:22:53PM +0000, Ian Campbell wrote: > > Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx> > > --- > > v6: Also discuss recovering the memory. > > > > v7: Further clarifications regarding forking based on ML discussions. > > ÂÂÂÂ(Dropped Wei's ack) > > --- > > Â.../libs/foreignmemory/include/xenforeignmemory.hÂÂ| 33 > > +++++++++++++++++++++- > > Â1 file changed, 32 insertions(+), 1 deletion(-) > > > > diff --git a/tools/libs/foreignmemory/include/xenforeignmemory.h > > b/tools/libs/foreignmemory/include/xenforeignmemory.h > > index 04ff548..a6d1bdb 100644 > > --- a/tools/libs/foreignmemory/include/xenforeignmemory.h > > +++ b/tools/libs/foreignmemory/include/xenforeignmemory.h > > @@ -32,13 +32,44 @@ typedef struct xentoollog_logger xentoollog_logger; > > Âtypedef struct xenforeignmemory_handle xenforeignmemory_handle; > > Â > > Â/* > > - * Return a handle onto the hypercall driver.ÂÂLogs errors. > > + * Return a handle onto the foreign memory mapping driver.ÂÂLogs > > errors. > > + * > > + * Note: After fork(2) a child process must not use any opened > > + * foreignmemory handle inherited from their parent, nor access any > > + * grant mapped areas associated with that handle. > > + * > > + * The child must open a new handle if they want to interact with > > + * foreignmemory. > > + * > > + * Calling exec(2) in a child will safely (and reliably) reclaim any > > + * resources which were allocated via a xenforeignmemory_handle in the > > + * parent. > > + * > > + * A child which does not call exec(2) may safely call > > + * xenforeignmemory_close() on a xenforeignmemory_handle inherited > > + * from their parent. This will attempt to reclaim any resources > > + * associated with that handle. Note that in some implementations this > > + * reclamation may not be completely effective, in this case any > > + * affected resources remain allocated. > > + * > > + * Calling xenforeignmemory_close() is the only safe operation on a > > + * xenforeignmemory_handle which has been inherited. > > Â */ > > Âxenforeignmemory_handle *xenforeignmemory_open(xentoollog_logger > > *logger, > > ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂunsigned open_flags); > > Â > > Â/* > > Â * Close a handle previously allocated with xenforeignmemory_open(). > > + * > > + * Under normal circumstances (i.e. not in the child after a fork) > > + * xenforeignmemory_unmap() should be used on all mappings allocated > > "Should" according to RFC 2119 has the connotation of "there might be a > valid reason to ignore such action". But after reading this passage I > think we should use "must" here? RFC 2119 formally defines "SHOULD" not "should" (or "Should"), and in any case in order to be subject to those formal definitions a document would need to explicitly reference RFC 2119. I think most readers of normal English prose would probably take "must" and "should" to mean mostly the same thing. If there are other reasons to resend I don't mind switching it to must, but I don't think it is worth a resend of this mega-series for what is a minor semantic quibble. Ian. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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