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path: root/include/block/graph-lock.h
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2023-06-28graph-lock: Unlock the AioContext while pollingKevin Wolf
If the caller keeps the AioContext lock for a block node in an iothread, polling in bdrv_graph_wrlock() deadlocks if the condition isn't fulfilled immediately. Now that all callers make sure to actually have the AioContext locked when they call bdrv_replace_child_noperm() like they should, we can change bdrv_graph_wrlock() to take a BlockDriverState whose AioContext lock the caller holds (NULL if it doesn't) and unlock it temporarily while polling. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Message-ID: <20230605085711.21261-11-kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2023-05-10graph-lock: Fix GRAPH_RDLOCK_GUARD*() to be reader lockKevin Wolf
GRAPH_RDLOCK_GUARD() and GRAPH_RDLOCK_GUARD_MAINLOOP() only take a reader lock for the graph, so the correct annotation for them to use is TSA_ASSERT_SHARED rather than TSA_ASSERT. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Message-Id: <20230504115750.54437-8-kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2023-05-10graph-lock: Add GRAPH_UNLOCKED(_PTR)Kevin Wolf
For some functions, it is part of their interface to be called without holding the graph lock. Add a new macro to document this. The macro expands to TSA_EXCLUDES(), which is a relatively weak check because it passes in cases where the compiler just doesn't know if the lock is held. Function pointers can't be checked at all. Therefore, its primary purpose is documentation. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Message-Id: <20230504115750.54437-7-kwolf@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2023-05-10block: add missing coroutine_fn annotationsPaolo Bonzini
After the recent introduction of many new coroutine callbacks, a couple calls from non-coroutine_fn to coroutine_fn have sneaked in; fix them. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <20230406101752.242125-1-pbonzini@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2023-02-08block: Clean up includesMarkus Armbruster
This commit was created with scripts/clean-includes. All .c should include qemu/osdep.h first. The script performs three related cleanups: * Ensure .c files include qemu/osdep.h first. * Including it in a .h is redundant, since the .c already includes it. Drop such inclusions. * Likewise, including headers qemu/osdep.h includes is redundant. Drop these, too. Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Message-Id: <20230202133830.2152150-16-armbru@redhat.com>
2023-01-19coroutine: Move coroutine_fn to qemu/osdep.h, trim includesMarkus Armbruster
block/block-hmp-cmds.h and qemu/co-shared-resource.h use coroutine_fn without including qemu/coroutine.h. They compile only if it's already included from elsewhere. I could fix that, but pulling in qemu/coroutine.h and everything it includes just for a macro that expands into nothing feels silly. Instead, move the macro to qemu/osdep.h. Inclusions of qemu/coroutine.h just for coroutine_fn become superfluous. Drop them. Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Message-Id: <20221221131435.3851212-3-armbru@redhat.com>
2022-12-15Mark assert_bdrv_graph_readable/writable() GRAPH_RD/WRLOCKKevin Wolf
Signed-off-by: Kevin Wolf <kwolf@redhat.com> Message-Id: <20221207131838.239125-16-kwolf@redhat.com> Reviewed-by: Emanuele Giuseppe Esposito <eesposit@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2022-12-15graph-lock: TSA annotations for lock/unlock functionsKevin Wolf
Signed-off-by: Kevin Wolf <kwolf@redhat.com> Message-Id: <20221207131838.239125-15-kwolf@redhat.com> Reviewed-by: Emanuele Giuseppe Esposito <eesposit@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2022-12-15block: assert that graph read and writes are performed correctlyEmanuele Giuseppe Esposito
Remove the old assert_bdrv_graph_writable, and replace it with the new version using graph-lock API. See the function documentation for more information. Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com> Message-Id: <20221207131838.239125-14-kwolf@redhat.com> Reviewed-by: Emanuele Giuseppe Esposito <eesposit@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2022-12-15graph-lock: Implement guard macrosEmanuele Giuseppe Esposito
Similar to the implementation in lockable.h, implement macros to automatically take and release the rdlock. Create the empty GraphLockable and GraphLockableMainloop structs only to use it as a type for G_DEFINE_AUTOPTR_CLEANUP_FUNC. Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com> Message-Id: <20221207131838.239125-4-kwolf@redhat.com> Reviewed-by: Emanuele Giuseppe Esposito <eesposit@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2022-12-15graph-lock: Introduce a lock to protect block graph operationsPaolo Bonzini
Block layer graph operations are always run under BQL in the main loop. This is proved by the assertion qemu_in_main_thread() and its wrapper macro GLOBAL_STATE_CODE. However, there are also concurrent coroutines running in other iothreads that always try to traverse the graph. Currently this is protected (among various other things) by the AioContext lock, but once this is removed, we need to make sure that reads do not happen while modifying the graph. We distinguish between writer (main loop, under BQL) that modifies the graph, and readers (all other coroutines running in various AioContext), that go through the graph edges, reading ->parents and->children. The writer (main loop) has "exclusive" access, so it first waits for any current read to finish, and then prevents incoming ones from entering while it has the exclusive access. The readers (coroutines in multiple AioContext) are free to access the graph as long the writer is not modifying the graph. In case it is, they go in a CoQueue and sleep until the writer is done. If a coroutine changes AioContext, the counter in the original and new AioContext are left intact, since the writer does not care where the reader is, but only if there is one. As a result, some AioContexts might have a negative reader count, to balance the positive count of the AioContext that took the lock. This also means that when an AioContext is deleted it may have a nonzero reader count. In that case we transfer the count to a global shared counter so that the writer is always aware of all readers. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com> Message-Id: <20221207131838.239125-3-kwolf@redhat.com> Reviewed-by: Emanuele Giuseppe Esposito <eesposit@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>