Re: [Libguestfs] [PATCH nbdkit 2/4] server: Add nbdkit_shutdown() call.
On 3/4/20 9:17 AM, Richard W.M. Jones wrote:
Plugins and filters may call this to initiate an asynchronous
shutdown
of the server. This would only be used in the connected phase —
plugins should still call exit(3) directly for configuration failure.
It is equivalent to sending a kill signal to self, but it's cleaner to
have an API for this and better for potential future non-POSIX platforms.
---
docs/nbdkit-plugin.pod | 19 +++++++-
include/nbdkit-common.h | 1 +
include/nbdkit-plugin.h | 2 +-
tests/Makefile.am | 20 ++++++++
server/nbdkit.syms | 3 +-
server/quit.c | 8 +++-
tests/test-shutdown.sh | 71 ++++++++++++++++++++++++++++
tests/test-shutdown-plugin.c | 89 ++++++++++++++++++++++++++++++++++++
8 files changed, 209 insertions(+), 4 deletions(-)
+++ b/tests/test-shutdown.sh
+# Start nbdkit with the shutdown plugin.
+start_nbdkit -P shutdown.pid -U $sock $plugin
+
+pid=`cat shutdown.pid`
+
+# Reads are fine, nbdkit should still be running afterwards.
+for i in 1 2 3; do
+ qemu-img info "nbd:unix:$sock"
qemu-img should support nbd+unix:///?socket=$sock URIs; any reason we
aren't using them here?
+++ b/tests/test-shutdown-plugin.c
+
+static int64_t
+shutdown_get_size (void *handle)
+{
+ return INT64_C (1024*1024);
This looks fishy. POSIX says that:
https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/stdint.h.html#t...
"The argument in any instance of these macros shall be an unsuffixed
integer constant with a value that does not exceed the limits for the
corresponding type.
...For example, if uint_least64_t is a name for the type unsigned long
long, then UINT64_C(0x123) might expand to the integer constant 0x123ULL."
In fact, in glibc's /usr/include/stdint.h, we have:
# if __WORDSIZE == 64
# define INT64_C(c) c ## L
# else
# define INT64_C(c) c ## LL
# endif
Your code works by sheer luck (expanding to the three tokens '1024',
'*', '1024L'), which in turn results in an expression with 64-bit type,
but in general, INT64_C should ONLY be used on a single literal value,
not an arbitrary expression.
But you really don't need to use INT64_C; we can just rely on C's
automatic type promotion to turn our 'int' expression 1024*1024 into the
proper int64_t return value.
Otherwise, this is a nice addition!
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org