diff options
| author | Stefan Hajnoczi <stefanha@redhat.com> | 2018-03-22 15:28:33 +0000 |
|---|---|---|
| committer | Stefan Hajnoczi <stefanha@redhat.com> | 2018-03-27 13:05:28 +0100 |
| commit | c40a2545700e9ad2ef67d5972484bbee4c83b2a6 (patch) | |
| tree | 2c550ddaf9a59a58c3c07e40c02aded945384cd1 /block/io.c | |
| parent | 67a74148d8828f611fc5a7a23277b8eceb4c9430 (diff) | |
coroutine: avoid co_queue_wakeup recursion
qemu_aio_coroutine_enter() is (indirectly) called recursively when
processing co_queue_wakeup. This can lead to stack exhaustion.
This patch rewrites co_queue_wakeup in an iterative fashion (instead of
recursive) with bounded memory usage to prevent stack exhaustion.
qemu_co_queue_run_restart() is inlined into qemu_aio_coroutine_enter()
and the qemu_coroutine_enter() call is turned into a loop to avoid
recursion.
There is one change that is worth mentioning: Previously, when
coroutine A queued coroutine B, qemu_co_queue_run_restart() entered
coroutine B from coroutine A. If A was terminating then it would still
stay alive until B yielded. After this patch B is entered by A's parent
so that a A can be deleted immediately if it is terminating.
It is safe to make this change since B could never interact with A if it
was terminating anyway.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 20180322152834.12656-3-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Diffstat (limited to 'block/io.c')
| -rw-r--r-- | block/io.c | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/block/io.c b/block/io.c index 2b09c656d0..bd9a19a9c4 100644 --- a/block/io.c +++ b/block/io.c @@ -249,8 +249,7 @@ static void coroutine_fn bdrv_co_yield_to_drain(BlockDriverState *bs, BdrvCoDrainData data; /* Calling bdrv_drain() from a BH ensures the current coroutine yields and - * other coroutines run if they were queued from - * qemu_co_queue_run_restart(). */ + * other coroutines run if they were queued by aio_co_enter(). */ assert(qemu_in_coroutine()); data = (BdrvCoDrainData) { |