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| author | Alexander Bulekov <alxndr@bu.edu> | 2023-04-27 17:10:07 -0400 |
|---|---|---|
| committer | Thomas Huth <thuth@redhat.com> | 2023-04-28 11:31:07 +0200 |
| commit | 9c86c97f12c060bf7484dd931f38634e166a81f0 (patch) | |
| tree | b3e82f9abe80c39166b4880f0405b0785ba731a5 /docs | |
| parent | a2e1753b8054344f32cf94f31c6399a58794a380 (diff) | |
| download | focaccia-qemu-9c86c97f12c060bf7484dd931f38634e166a81f0.tar.gz focaccia-qemu-9c86c97f12c060bf7484dd931f38634e166a81f0.zip | |
async: Add an optional reentrancy guard to the BH API
Devices can pass their MemoryReentrancyGuard (from their DeviceState), when creating new BHes. Then, the async API will toggle the guard before/after calling the BH call-back. This prevents bh->mmio reentrancy issues. Signed-off-by: Alexander Bulekov <alxndr@bu.edu> Reviewed-by: Darren Kenny <darren.kenny@oracle.com> Message-Id: <20230427211013.2994127-3-alxndr@bu.edu> [thuth: Fix "line over 90 characters" checkpatch.pl error] Signed-off-by: Thomas Huth <thuth@redhat.com>
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/devel/multiple-iothreads.txt | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/docs/devel/multiple-iothreads.txt b/docs/devel/multiple-iothreads.txt index 343120f2ef..a3e949f6b3 100644 --- a/docs/devel/multiple-iothreads.txt +++ b/docs/devel/multiple-iothreads.txt @@ -61,6 +61,7 @@ There are several old APIs that use the main loop AioContext: * LEGACY qemu_aio_set_event_notifier() - monitor an event notifier * LEGACY timer_new_ms() - create a timer * LEGACY qemu_bh_new() - create a BH + * LEGACY qemu_bh_new_guarded() - create a BH with a device re-entrancy guard * LEGACY qemu_aio_wait() - run an event loop iteration Since they implicitly work on the main loop they cannot be used in code that @@ -72,8 +73,14 @@ Instead, use the AioContext functions directly (see include/block/aio.h): * aio_set_event_notifier() - monitor an event notifier * aio_timer_new() - create a timer * aio_bh_new() - create a BH + * aio_bh_new_guarded() - create a BH with a device re-entrancy guard * aio_poll() - run an event loop iteration +The qemu_bh_new_guarded/aio_bh_new_guarded APIs accept a "MemReentrancyGuard" +argument, which is used to check for and prevent re-entrancy problems. For +BHs associated with devices, the reentrancy-guard is contained in the +corresponding DeviceState and named "mem_reentrancy_guard". + The AioContext can be obtained from the IOThread using iothread_get_aio_context() or for the main loop using qemu_get_aio_context(). Code that takes an AioContext argument works both in IOThreads or the main |