[RFC,v3,02/45] multi-process: util: Add qemu_thread_cancel() to cancel running thread

Commit Message

Jag Raman Sept. 3, 2019, 8:37 p.m. UTC

qemu_thread_cancel() added to destroy a given running thread.
This will be needed in the following patches.

Signed-off-by: John G Johnson <[e-mail]>
Signed-off-by: Jagannathan Raman <[e-mail]>
Signed-off-by: Elena Ufimtseva <[e-mail]>
---
 include/qemu/thread.h    |  1 +
 util/qemu-thread-posix.c | 10 ++++++++++
 2 files changed, 11 insertions(+)

Comments

Daniel P. Berrangé Sept. 4, 2019, 9:11 a.m. UTC | #1

On Tue, Sep 03, 2019 at 04:37:28PM -0400, Jagannathan Raman wrote:
> qemu_thread_cancel() added to destroy a given running thread.
> This will be needed in the following patches.

I don't see anything in the following patches that actually uses
this new function.

That is good though, because it is incredibly difficult to
correctly use pthread_cancel() in such a way that you correctly
release all memory and other resources (file descriptors) owned
by the thread being cancelled.

So this looks like it can thankfully be dropped.

> 
> Signed-off-by: John G Johnson <[e-mail]>
> Signed-off-by: Jagannathan Raman <[e-mail]>
> Signed-off-by: Elena Ufimtseva <[e-mail]>
> ---
>  include/qemu/thread.h    |  1 +
>  util/qemu-thread-posix.c | 10 ++++++++++
>  2 files changed, 11 insertions(+)

Regards,
Daniel

Jag Raman Sept. 5, 2019, 3:10 p.m. UTC | #2

On 9/4/2019 5:11 AM, Daniel P. Berrangé wrote:
> On Tue, Sep 03, 2019 at 04:37:28PM -0400, Jagannathan Raman wrote:
>> qemu_thread_cancel() added to destroy a given running thread.
>> This will be needed in the following patches.
> 
> I don't see anything in the following patches that actually uses
> this new function.
> 
> That is good though, because it is incredibly difficult to
> correctly use pthread_cancel() in such a way that you correctly
> release all memory and other resources (file descriptors) owned
> by the thread being cancelled.
> 
> So this looks like it can thankfully be dropped.

Thanks Daniel. Will drop this in the next revision.
--
Jag

> 
>>
>> Signed-off-by: John G Johnson <[e-mail]>
>> Signed-off-by: Jagannathan Raman <[e-mail]>
>> Signed-off-by: Elena Ufimtseva <[e-mail]>
>> ---
>>   include/qemu/thread.h    |  1 +
>>   util/qemu-thread-posix.c | 10 ++++++++++
>>   2 files changed, 11 insertions(+)
> 
> Regards,
> Daniel
>

Patch

diff --git a/include/qemu/thread.h b/include/qemu/thread.h
index 55d83a9..78791be 100644
--- a/include/qemu/thread.h
+++ b/include/qemu/thread.h
@@ -156,6 +156,7 @@  void qemu_thread_create(QemuThread *thread, const char *name,
                         void *(*start_routine)(void *),
                         void *arg, int mode);
 void *qemu_thread_join(QemuThread *thread);
+void qemu_thread_cancel(QemuThread *thread);
 void qemu_thread_get_self(QemuThread *thread);
 bool qemu_thread_is_self(QemuThread *thread);
 void qemu_thread_exit(void *retval);
diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c
index 1bf5e65..7c89071 100644
--- a/util/qemu-thread-posix.c
+++ b/util/qemu-thread-posix.c
@@ -573,3 +573,13 @@  void *qemu_thread_join(QemuThread *thread)
     }
     return ret;
 }
+
+void qemu_thread_cancel(QemuThread *thread)
+{
+    int err;
+
+    err = pthread_cancel(thread->thread);
+    if (err) {
+        error_exit(err, __func__);
+    }
+}