Re: [Qemu-devel] [PATCH 2/3] migration: Use automatic rcu_read unlock in ram.c

[Dr. David Alan Gilbert]

* Daniel P. Berrangé (berra...@redhat.com) wrote:
> On Wed, Sep 11, 2019 at 05:42:01PM +0100, Dr. David Alan Gilbert (git) wrote:
> > From: "Dr. David Alan Gilbert" 
> > 
> > Use the automatic read unlocker in migration/ram.c;
> > only for the cases where the unlock is at the end of the function.
> > 
> > Signed-off-by: Dr. David Alan Gilbert 
> > ---
> >  migration/ram.c | 25 +
> >  1 file changed, 9 insertions(+), 16 deletions(-)
> > 
> > diff --git a/migration/ram.c b/migration/ram.c
> > index b2bd618a89..750d198f37 100644
> > --- a/migration/ram.c
> > +++ b/migration/ram.c
> > @@ -181,14 +181,14 @@ int foreach_not_ignored_block(RAMBlockIterFunc func, 
> > void *opaque)
> >  RAMBlock *block;
> >  int ret = 0;
> >  
> > -rcu_read_lock();
> > +RCU_READ_LOCK_AUTO
> 
> FWIW, I'm not a fan of macros which are used without a trailing ';'
> as I believe it can confuses editors' code indentation logic.

Added.

> 
> Regards,
> Daniel
> -- 
> |: https://berrange.com  -o-https://www.flickr.com/photos/dberrange :|
> |: https://libvirt.org -o-https://fstop138.berrange.com :|
> |: https://entangle-photo.org-o-https://www.instagram.com/dberrange :|
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK

Re: [Qemu-devel] [PATCH 2/3] migration: Use automatic rcu_read unlock in ram.c

[Daniel P . Berrangé]

On Wed, Sep 11, 2019 at 05:42:01PM +0100, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" 
> 
> Use the automatic read unlocker in migration/ram.c;
> only for the cases where the unlock is at the end of the function.
> 
> Signed-off-by: Dr. David Alan Gilbert 
> ---
>  migration/ram.c | 25 +
>  1 file changed, 9 insertions(+), 16 deletions(-)
> 
> diff --git a/migration/ram.c b/migration/ram.c
> index b2bd618a89..750d198f37 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -181,14 +181,14 @@ int foreach_not_ignored_block(RAMBlockIterFunc func, 
> void *opaque)
>  RAMBlock *block;
>  int ret = 0;
>  
> -rcu_read_lock();
> +RCU_READ_LOCK_AUTO

FWIW, I'm not a fan of macros which are used without a trailing ';'
as I believe it can confuses editors' code indentation logic.


Regards,
Daniel
-- 
|: https://berrange.com  -o-https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org -o-https://fstop138.berrange.com :|
|: https://entangle-photo.org-o-https://www.instagram.com/dberrange :|

[Qemu-devel] [PATCH 2/3] migration: Use automatic rcu_read unlock in ram.c

[Dr. David Alan Gilbert (git)]

From: "Dr. David Alan Gilbert" 

Use the automatic read unlocker in migration/ram.c;
only for the cases where the unlock is at the end of the function.

Signed-off-by: Dr. David Alan Gilbert 
---
 migration/ram.c | 25 +
 1 file changed, 9 insertions(+), 16 deletions(-)

diff --git a/migration/ram.c b/migration/ram.c
index b2bd618a89..750d198f37 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -181,14 +181,14 @@ int foreach_not_ignored_block(RAMBlockIterFunc func, void 
*opaque)
 RAMBlock *block;
 int ret = 0;
 
-rcu_read_lock();
+RCU_READ_LOCK_AUTO
+
 RAMBLOCK_FOREACH_NOT_IGNORED(block) {
 ret = func(block, opaque);
 if (ret) {
 break;
 }
 }
-rcu_read_unlock();
 return ret;
 }
 
@@ -2398,13 +2398,12 @@ static void migration_page_queue_free(RAMState *rs)
 /* This queue generally should be empty - but in the case of a failed
  * migration might have some droppings in.
  */
-rcu_read_lock();
+RCU_READ_LOCK_AUTO
 QSIMPLEQ_FOREACH_SAFE(mspr, >src_page_requests, next_req, next_mspr) {
 memory_region_unref(mspr->rb->mr);
 QSIMPLEQ_REMOVE_HEAD(>src_page_requests, next_req);
 g_free(mspr);
 }
-rcu_read_unlock();
 }
 
 /**
@@ -2425,7 +2424,8 @@ int ram_save_queue_pages(const char *rbname, ram_addr_t 
start, ram_addr_t len)
 RAMState *rs = ram_state;
 
 ram_counters.postcopy_requests++;
-rcu_read_lock();
+RCU_READ_LOCK_AUTO
+
 if (!rbname) {
 /* Reuse last RAMBlock */
 ramblock = rs->last_req_rb;
@@ -2467,12 +2467,10 @@ int ram_save_queue_pages(const char *rbname, ram_addr_t 
start, ram_addr_t len)
 QSIMPLEQ_INSERT_TAIL(>src_page_requests, new_entry, next_req);
 migration_make_urgent_request();
 qemu_mutex_unlock(>src_page_req_mutex);
-rcu_read_unlock();
 
 return 0;
 
 err:
-rcu_read_unlock();
 return -1;
 }
 
@@ -2712,7 +2710,8 @@ static uint64_t ram_bytes_total_common(bool count_ignored)
 RAMBlock *block;
 uint64_t total = 0;
 
-rcu_read_lock();
+RCU_READ_LOCK_AUTO
+
 if (count_ignored) {
 RAMBLOCK_FOREACH_MIGRATABLE(block) {
 total += block->used_length;
@@ -2722,7 +2721,6 @@ static uint64_t ram_bytes_total_common(bool count_ignored)
 total += block->used_length;
 }
 }
-rcu_read_unlock();
 return total;
 }
 
@@ -3086,7 +3084,7 @@ int ram_postcopy_send_discard_bitmap(MigrationState *ms)
 RAMBlock *block;
 int ret;
 
-rcu_read_lock();
+RCU_READ_LOCK_AUTO
 
 /* This should be our last sync, the src is now paused */
 migration_bitmap_sync(rs);
@@ -3107,13 +3105,11 @@ int ram_postcopy_send_discard_bitmap(MigrationState *ms)
  * point.
  */
 error_report("migration ram resized during precopy phase");
-rcu_read_unlock();
 return -EINVAL;
 }
 /* Deal with TPS != HPS and huge pages */
 ret = postcopy_chunk_hostpages(ms, block);
 if (ret) {
-rcu_read_unlock();
 return ret;
 }
 
@@ -3128,7 +3124,6 @@ int ram_postcopy_send_discard_bitmap(MigrationState *ms)
 trace_ram_postcopy_send_discard_bitmap();
 
 ret = postcopy_each_ram_send_discard(ms);
-rcu_read_unlock();
 
 return ret;
 }
@@ -3149,7 +3144,7 @@ int ram_discard_range(const char *rbname, uint64_t start, 
size_t length)
 
 trace_ram_discard_range(rbname, start, length);
 
-rcu_read_lock();
+RCU_READ_LOCK_AUTO
 RAMBlock *rb = qemu_ram_block_by_name(rbname);
 
 if (!rb) {
@@ -3169,8 +3164,6 @@ int ram_discard_range(const char *rbname, uint64_t start, 
size_t length)
 ret = ram_block_discard_range(rb, start, length);
 
 err:
-rcu_read_unlock();
-
 return ret;
 }
 
-- 
2.21.0