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[PATCH 2/2] nbd: disable signals and forking on Windows builds

Daniel P. Berrangé posted 2 patches 5 years, 5 months ago
There is a newer version of this series
[PATCH 2/2] nbd: disable signals and forking on Windows builds
Posted by Daniel P. Berrangé 5 years, 5 months ago 
Disabling these parts are sufficient to get the qemu-nbd program
compiling in a Windows build.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 meson.build |  7 ++-----
 qemu-nbd.c  | 10 +++++++++-
 2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/meson.build b/meson.build
index df5bf728b5..1071871605 100644
--- a/meson.build
+++ b/meson.build
@@ -1074,12 +1074,9 @@ if have_tools
              dependencies: [authz, block, crypto, io, qom, qemuutil], install: true)
   qemu_io = executable('qemu-io', files('qemu-io.c'),
              dependencies: [block, qemuutil], install: true)
-  qemu_block_tools += [qemu_img, qemu_io]
-  if targetos == 'linux' or targetos == 'sunos' or targetos.endswith('bsd')
-    qemu_nbd = executable('qemu-nbd', files('qemu-nbd.c'),
+  qemu_nbd = executable('qemu-nbd', files('qemu-nbd.c'),
                dependencies: [block, qemuutil], install: true)
-    qemu_block_tools += [qemu_nbd]
-  endif
+  qemu_block_tools += [qemu_img, qemu_io, qemu_nbd]
 
   subdir('storage-daemon')
   subdir('contrib/rdmacm-mux')
diff --git a/qemu-nbd.c b/qemu-nbd.c
index b102874f0f..c6fd6524d3 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -155,12 +155,13 @@ QEMU_COPYRIGHT "\n"
     , name);
 }
 
+#ifndef WIN32
 static void termsig_handler(int signum)
 {
     atomic_cmpxchg(&state, RUNNING, TERMINATE);
     qemu_notify_event();
 }
-
+#endif
 
 static int qemu_nbd_client_list(SocketAddress *saddr, QCryptoTLSCreds *tls,
                                 const char *hostname)
@@ -587,6 +588,7 @@ int main(int argc, char **argv)
     unsigned socket_activation;
     const char *pid_file_name = NULL;
 
+#ifndef WIN32
     /* The client thread uses SIGTERM to interrupt the server.  A signal
      * handler ensures that "qemu-nbd -v -c" exits with a nice status code.
      */
@@ -594,6 +596,7 @@ int main(int argc, char **argv)
     memset(&sa_sigterm, 0, sizeof(sa_sigterm));
     sa_sigterm.sa_handler = termsig_handler;
     sigaction(SIGTERM, &sa_sigterm, NULL);
+#endif
 
 #ifdef CONFIG_POSIX
     signal(SIGPIPE, SIG_IGN);
@@ -896,6 +899,7 @@ int main(int argc, char **argv)
 #endif
 
     if ((device && !verbose) || fork_process) {
+#ifndef WIN32
         int stderr_fd[2];
         pid_t pid;
         int ret;
@@ -959,6 +963,10 @@ int main(int argc, char **argv)
              */
             exit(errors);
         }
+#else /* WIN32 */
+        error_report("Unable to fork into background on Windows hosts");
+        exit(EXIT_FAILURE);
+#endif /* WIN32 */
     }
 
     if (device != NULL && sockpath == NULL) {
-- 
2.26.2
Re: [PATCH 2/2] nbd: disable signals and forking on Windows builds
Posted by Eric Blake 5 years, 5 months ago 
On 8/24/20 12:02 PM, Daniel P. Berrangé wrote:
> Disabling these parts are sufficient to get the qemu-nbd program
> compiling in a Windows build.
> 
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> ---
>   meson.build |  7 ++-----
>   qemu-nbd.c  | 10 +++++++++-
>   2 files changed, 11 insertions(+), 6 deletions(-)

Feels a bit hacky at what it supports, but certainly better than nothing ;)

> 
> diff --git a/meson.build b/meson.build
> index df5bf728b5..1071871605 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -1074,12 +1074,9 @@ if have_tools
>                dependencies: [authz, block, crypto, io, qom, qemuutil], install: true)
>     qemu_io = executable('qemu-io', files('qemu-io.c'),
>                dependencies: [block, qemuutil], install: true)
> -  qemu_block_tools += [qemu_img, qemu_io]
> -  if targetos == 'linux' or targetos == 'sunos' or targetos.endswith('bsd')
> -    qemu_nbd = executable('qemu-nbd', files('qemu-nbd.c'),
> +  qemu_nbd = executable('qemu-nbd', files('qemu-nbd.c'),
>                  dependencies: [block, qemuutil], install: true)

Conflicts with this patch:
https://lists.gnu.org/archive/html/qemu-devel/2020-08/msg05546.html

but this one gets rid of the need for that one.

> -    qemu_block_tools += [qemu_nbd]
> -  endif
> +  qemu_block_tools += [qemu_img, qemu_io, qemu_nbd]
>   
>     subdir('storage-daemon')
>     subdir('contrib/rdmacm-mux')
> diff --git a/qemu-nbd.c b/qemu-nbd.c
> index b102874f0f..c6fd6524d3 100644
> --- a/qemu-nbd.c
> +++ b/qemu-nbd.c
> @@ -155,12 +155,13 @@ QEMU_COPYRIGHT "\n"
>       , name);
>   }
>   
> +#ifndef WIN32
>   static void termsig_handler(int signum)
>   {
>       atomic_cmpxchg(&state, RUNNING, TERMINATE);
>       qemu_notify_event();
>   }
> -
> +#endif

How does one terminate a long-running server on Windows if there is no 
SIGTERM handler?  I guess Ctrl-C does something, but without the state 
notification from a signal handler, you are getting less-clean 
shutdowns, which may explain the hangs you were seeing in testing?  But 
incremental progress is fine, and I see no reason to not take this patch 
as-is.

Reviewed-by: Eric Blake <eblake@redhat.com>

I'm happy to queue this series through my NBD tree.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org
Re: [PATCH 2/2] nbd: disable signals and forking on Windows builds
Posted by Daniel P. Berrangé 5 years, 5 months ago 
On Mon, Aug 24, 2020 at 12:12:53PM -0500, Eric Blake wrote:
> On 8/24/20 12:02 PM, Daniel P. Berrangé wrote:
> > Disabling these parts are sufficient to get the qemu-nbd program
> > compiling in a Windows build.
> > 
> > Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> > ---
> >   meson.build |  7 ++-----
> >   qemu-nbd.c  | 10 +++++++++-
> >   2 files changed, 11 insertions(+), 6 deletions(-)
> 
> Feels a bit hacky at what it supports, but certainly better than nothing ;)
> 
> > 
> > diff --git a/meson.build b/meson.build
> > index df5bf728b5..1071871605 100644
> > --- a/meson.build
> > +++ b/meson.build
> > @@ -1074,12 +1074,9 @@ if have_tools
> >                dependencies: [authz, block, crypto, io, qom, qemuutil], install: true)
> >     qemu_io = executable('qemu-io', files('qemu-io.c'),
> >                dependencies: [block, qemuutil], install: true)
> > -  qemu_block_tools += [qemu_img, qemu_io]
> > -  if targetos == 'linux' or targetos == 'sunos' or targetos.endswith('bsd')
> > -    qemu_nbd = executable('qemu-nbd', files('qemu-nbd.c'),
> > +  qemu_nbd = executable('qemu-nbd', files('qemu-nbd.c'),
> >                  dependencies: [block, qemuutil], install: true)
> 
> Conflicts with this patch:
> https://lists.gnu.org/archive/html/qemu-devel/2020-08/msg05546.html
> 
> but this one gets rid of the need for that one.
> 
> > -    qemu_block_tools += [qemu_nbd]
> > -  endif
> > +  qemu_block_tools += [qemu_img, qemu_io, qemu_nbd]
> >     subdir('storage-daemon')
> >     subdir('contrib/rdmacm-mux')
> > diff --git a/qemu-nbd.c b/qemu-nbd.c
> > index b102874f0f..c6fd6524d3 100644
> > --- a/qemu-nbd.c
> > +++ b/qemu-nbd.c
> > @@ -155,12 +155,13 @@ QEMU_COPYRIGHT "\n"
> >       , name);
> >   }
> > +#ifndef WIN32
> >   static void termsig_handler(int signum)
> >   {
> >       atomic_cmpxchg(&state, RUNNING, TERMINATE);
> >       qemu_notify_event();
> >   }
> > -
> > +#endif
> 
> How does one terminate a long-running server on Windows if there is no
> SIGTERM handler?  I guess Ctrl-C does something, but without the state
> notification from a signal handler, you are getting less-clean shutdowns,
> which may explain the hangs you were seeing in testing?  But incremental
> progress is fine, and I see no reason to not take this patch as-is.

The hangs occurred even with windows client/ native server, just less
frequently so don't think it is related.

Re-reading the code I notice this SIGTERM handler is only there for
the NBD device client thread, so we should skip it if that is not
installed.

Ctrl-C does SIGINT, so that's unrelated to the SIGTERM handler.

> 
> Reviewed-by: Eric Blake <eblake@redhat.com>
> 
> I'm happy to queue this series through my NBD tree.

I'll post a v2

Regards,
Daniel
-- 
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Re: [PATCH 2/2] nbd: disable signals and forking on Windows builds
Posted by Thomas Huth 5 years, 5 months ago 
On 24/08/2020 19.02, Daniel P. Berrangé wrote:
> Disabling these parts are sufficient to get the qemu-nbd program
> compiling in a Windows build.

Maybe add:
"This also enables compilation of qemu-nbd on macOS again (which got 
disabled by accident during the conversion to the meson build system)"

> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> ---
>   meson.build |  7 ++-----
>   qemu-nbd.c  | 10 +++++++++-
>   2 files changed, 11 insertions(+), 6 deletions(-)
> 
> diff --git a/meson.build b/meson.build
> index df5bf728b5..1071871605 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -1074,12 +1074,9 @@ if have_tools
>                dependencies: [authz, block, crypto, io, qom, qemuutil], install: true)
>     qemu_io = executable('qemu-io', files('qemu-io.c'),
>                dependencies: [block, qemuutil], install: true)
> -  qemu_block_tools += [qemu_img, qemu_io]
> -  if targetos == 'linux' or targetos == 'sunos' or targetos.endswith('bsd')
> -    qemu_nbd = executable('qemu-nbd', files('qemu-nbd.c'),
> +  qemu_nbd = executable('qemu-nbd', files('qemu-nbd.c'),
>                  dependencies: [block, qemuutil], install: true)
> -    qemu_block_tools += [qemu_nbd]
> -  endif
> +  qemu_block_tools += [qemu_img, qemu_io, qemu_nbd]
>   
>     subdir('storage-daemon')
>     subdir('contrib/rdmacm-mux')
> diff --git a/qemu-nbd.c b/qemu-nbd.c
> index b102874f0f..c6fd6524d3 100644
> --- a/qemu-nbd.c
> +++ b/qemu-nbd.c
> @@ -155,12 +155,13 @@ QEMU_COPYRIGHT "\n"
>       , name);
>   }
>   
> +#ifndef WIN32
>   static void termsig_handler(int signum)
>   {
>       atomic_cmpxchg(&state, RUNNING, TERMINATE);
>       qemu_notify_event();
>   }
> -
> +#endif
>   
>   static int qemu_nbd_client_list(SocketAddress *saddr, QCryptoTLSCreds *tls,
>                                   const char *hostname)
> @@ -587,6 +588,7 @@ int main(int argc, char **argv)
>       unsigned socket_activation;
>       const char *pid_file_name = NULL;
>   
> +#ifndef WIN32
>       /* The client thread uses SIGTERM to interrupt the server.  A signal
>        * handler ensures that "qemu-nbd -v -c" exits with a nice status code.
>        */
> @@ -594,6 +596,7 @@ int main(int argc, char **argv)
>       memset(&sa_sigterm, 0, sizeof(sa_sigterm));
>       sa_sigterm.sa_handler = termsig_handler;
>       sigaction(SIGTERM, &sa_sigterm, NULL);
> +#endif
>   
>   #ifdef CONFIG_POSIX

I wonder why the CONFIG_POSIX does not simply start earlier here ... I 
think you could replace your #ifndef WIN32 with #ifdef CONFIG_POSIX that 
way?

>       signal(SIGPIPE, SIG_IGN);
> @@ -896,6 +899,7 @@ int main(int argc, char **argv)
>   #endif
>   
>       if ((device && !verbose) || fork_process) {
> +#ifndef WIN32
>           int stderr_fd[2];
>           pid_t pid;
>           int ret;
> @@ -959,6 +963,10 @@ int main(int argc, char **argv)
>                */
>               exit(errors);
>           }
> +#else /* WIN32 */
> +        error_report("Unable to fork into background on Windows hosts");
> +        exit(EXIT_FAILURE);
> +#endif /* WIN32 */
>       }
>   
>       if (device != NULL && sockpath == NULL) {
> 

  Thomas

Patchew 2.1-devel-b67e4c2

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