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Re: [Qemu-stable] [PATCH v2 1/1] qemu-img: wait for convert coroutines t


From: Anton Nefedov
Subject: Re: [Qemu-stable] [PATCH v2 1/1] qemu-img: wait for convert coroutines to complete
Date: Fri, 21 Apr 2017 15:19:24 +0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0

On 04/21/2017 01:44 PM, Peter Lieven wrote:
Am 21.04.2017 um 12:04 schrieb Anton Nefedov:
On error path (like i/o error in one of the coroutines), it's required to
  - wait for coroutines completion before cleaning the common structures
  - reenter dependent coroutines so they ever finish

Introduced in 2d9187bc65.

Signed-off-by: Anton Nefedov <address@hidden>
---
[..]



And what if we error out in the read path? Wouldn't be something like this 
easier?


diff --git a/qemu-img.c b/qemu-img.c
index 22f559a..4ff1085 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -1903,6 +1903,16 @@ static int convert_do_copy(ImgConvertState *s)
         main_loop_wait(false);
     }

+    /* on error path we need to enter all coroutines that are still
+     * running before cleaning up common structures */
+    if (s->ret) {
+        for (i = 0; i < s->num_coroutines; i++) {
+             if (s->co[i]) {
+                 qemu_coroutine_enter(s->co[i]);
+             }
+        }
+    }
+
     if (s->compressed && !s->ret) {
         /* signal EOF to align */
         ret = blk_pwrite_compressed(s->target, 0, NULL, 0);


Peter


seemed a bit too daring to me to re-enter every coroutine potentially including the ones that yielded waiting for I/O completion.
If that's ok - that is for sure easier :)

Or maybe some intermediate variant, as you suggest but only enter the "wait_sector" coroutines (and main_loop_wait for the rest)?
Or do not even re-enter them, like just

-    while (s->ret == -EINPROGRESS) {
+    while (s->running_coroutines != s->waiting_coroutines) {
         main_loop_wait(false);
     }


/Anton



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