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[ Upstream commit 44b73962cb25f1c8170ea695c4564b05a75e1fd4 ] When a process dies, failed reply is sent to the sender of any transaction queued on a dead thread's todo list. The sender asserts that the received failed reply corresponds to the head of the transaction stack. This assert can fail if the dead thread is allowed to send outgoing transactions when there is already a transaction on its todo list, because this new transaction can end up on the transaction stack of the original sender. The following steps illustrate how this assertion can fail. 1. Thread1 sends txn19 to Thread2 (T1->transaction_stack=txn19, T2->todo+=txn19) 2. Without processing todo list, Thread2 sends txn20 to Thread1 (T1->todo+=txn20, T2->transaction_stack=txn20) 3. T1 processes txn20 on its todo list (T1->transaction_stack=txn20->txn19, T1->todo=<empty>) 4. T2 dies, T2->todo cleanup attempts to send failed reply for txn19, but T1->transaction_stack points to txn20 -- assertion failes Step 2. is the incorrect behavior. When there is a transaction on a thread's todo list, this thread should not be able to send any outgoing synchronous transactions. Only the head of the todo list needs to be checked because only threads that are waiting for proc work can directly receive work from another thread, and no work is allowed to be queued on such a thread without waking up the thread. This patch also enforces that a thread is not waiting for proc work when a work is directly enqueued to its todo list. Acked-by: Arve Hjønnevåg <arve@android.com> Reviewed-by: Martijn Coenen <maco@android.com> Signed-off-by: Sherry Yang <sherryy@android.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org> Change-Id: Ief18e5c6e478ae7347b4e7c4a955edb8841cf17f Signed-off-by: Richard Raya <rdxzv.dev@gmail.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.