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block/iscsi: use a bh to schedule co reentrance 

this fixes a potential segfault and performance regression.

If the coroutine is reentered directly in the iscsi_co_generic_cb
iscsi_process_{read,write} are interrupted and reentered any
time later. One the one hand this could happen after an iscsi_close
where the iscsi context is already gone (segfault). On the
other hand this limits the number of processed callbacks
in each aio_dispatch to one (potential performance regression).

Cc: qemu-stable@nongnu.org
Signed-off-by: Peter Lieven <pl@kamp.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit 8b9dfe9098)

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
This commit is contained in:
Peter Lieven 2013-12-14 17:31:40 +01:00 committed by Michael Roth
parent 9692bad34d
commit 02e1c55ddd
1 changed files with 10 additions and 1 deletions
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11
block/iscsi.c
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@ -65,6 +65,7 @@ typedef struct IscsiTask {
int do_retry; int do_retry;
struct scsi_task *task; struct scsi_task *task;
Coroutine *co; Coroutine *co;
QEMUBH *bh;
} IscsiTask; } IscsiTask;
typedef struct IscsiAIOCB { typedef struct IscsiAIOCB {
@ -121,6 +122,13 @@ iscsi_schedule_bh(IscsiAIOCB *acb)
qemu_bh_schedule(acb->bh); qemu_bh_schedule(acb->bh);
} }
static void iscsi_co_generic_bh_cb(void *opaque)
{
struct IscsiTask *iTask = opaque;
qemu_bh_delete(iTask->bh);
qemu_coroutine_enter(iTask->co, NULL);
}
static void static void
iscsi_co_generic_cb(struct iscsi_context *iscsi, int status, iscsi_co_generic_cb(struct iscsi_context *iscsi, int status,
void *command_data, void *opaque) void *command_data, void *opaque)
@ -145,7 +153,8 @@ iscsi_co_generic_cb(struct iscsi_context *iscsi, int status,
out: out:
if (iTask->co) { if (iTask->co) {
qemu_coroutine_enter(iTask->co, NULL); iTask->bh = qemu_bh_new(iscsi_co_generic_bh_cb, iTask);
qemu_bh_schedule(iTask->bh);
} }
} }