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When the host is frozen in SCSI EH state, at any point after the LLDD sets SAS_TASK_STATE_DONE for the sas_task task state, libsas may free the task; see sas_scsi_find_task(). This puts the LLDD in a difficult position, in that once it sets SAS_TASK_STATE_DONE for the task state it should not reference the sas_task again. But the LLDD needs will check the sas_task indirectly in calling task->task_done()->sas_scsi_task_done() or sas_ata_task_done() (to check if the host is frozen state actually). And the LLDD cannot set SAS_TASK_STATE_DONE for the task state after task->task_done() is called (as the sas_task is free'd at this point). This situation would seem to be a problem made by libsas. To work around, check in the LLDD whether the host is in frozen state to ensure it is ok to call task->task_done() function. If in the frozen state, we rely on SCSI EH and libsas to free the sas_task directly. We do not do this for the following IO types: - SMP - they are managed in libsas directly, outside SCSI EH - Any internally originated IO, for similar reason Signed-off-by: Xiang Chen <chenxiang66@hisilicon.com> Signed-off-by: John Garry <john.garry@huawei.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
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.