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b0935ef9b2
The VFS library can be used in single-threaded or multi-threaded environments and depending on that, signals are handled by the same thread which uses the VFS library or possibly by a different thread. If a VFS plugin needs to block to wait for a signal, there is currently no way which works reliably in both environments. For this reason, this commit makes the interface of the VFS library nonblocking, similar to the File_system session interface. The most important changes are: - Directories are created and opened with the 'opendir()' function and the directory entries are read with the recently introduced 'queue_read()' and 'complete_read()' functions. - Symbolic links are created and opened with the 'openlink()' function and the link target is read with the 'queue_read()' and 'complete_read()' functions and written with the 'write()' function. - The 'write()' function does not wait for signals anymore. This can have the effect that data written by a VFS library user has not been processed by a file system server yet when the library user asks for the size of the file or closes it (both done with RPC functions at the file system server). For this reason, a user of the VFS library should request synchronization before calling 'stat()' or 'close()'. To make sure that a file system server has processed all write request packets which a client submitted before the synchronization request, synchronization is now requested at the file system server with a synchronization packet instead of an RPC function. Because of this change, the synchronization interface of the VFS library is now split into 'queue_sync()' and 'complete_sync()' functions. Fixes #2399 |
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| .. | ||
| buffer.h | ||
| chunk.h | ||
| directory.h | ||
| file.h | ||
| followed_subject.h | ||
| main.cc | ||
| node.h | ||
| README | ||
| symlink.h | ||
| target.mk | ||
| trace_files.h | ||
The new _trace_fs_ server provides access to a trace session by providing a
file-system session as front end. Combined with Noux, it allows for the
interactive exploration and tracing of Genode's process tree using
traditional Unix tools.
Each trace subject is represented by a directory ('thread_name.subject') that
contains specific files, which are used to control the tracing process of the
thread as well as storing the content of its trace buffer:
:'enable': The tracing of a thread is activated if there is a valid policy
installed and the intend to trace the subject was made clear by writing '1'
to the 'enable' file. The tracing of a thread may be deactivated by writing a
'0' to this file.
:'policy': A policy may be changed by overwriting the currently used one in the
'policy' file. In this case, the old policy is replaced by the new one and
automatically used by the framework.
:'buffer_size': Writing a value to the 'buffer_size' file changes the size of
the trace buffer. This value is evaluated only when reactivating the tracing
of the thread.
:'events': The trace-buffer contents may be accessed by reading from the
'events' file. New trace events are appended to this file.
:'active': Reading the file will return whether the tracing is active (1) or
not (0).
:'cleanup': Nodes of untraced subjects are kept as long as they do not change
their tracing state to dead. Dead untraced nodes are automatically removed
from the file system. Subjects that were traced before and are now untraced
can be removed by writing '1' to the 'cleanup' file.
To use the trace_fs, a configuration similar to the following may be used:
! <start name="trace_fs">
! <resource name="RAM" quantum="128M"/>
! <provides><service name="File_system"/></provides>
! <config>
! <policy label_prefix="noux -> trace"
! interval="1000"
! subject_limit="512"
! trace_quota="64M" />
! </config>
! </start>
:'interval': sets the period the Trace_session is polled. The
time is given in milliseconds.
:'subject_limit': specifies how many trace subjects should by acquired at
max when the Trace_session is polled.
:'trace_quota': is the amount of quota the trace_fs should use for the
Trace_session connection. The remaining amount of RAM quota will be used
for the actual nodes of the file system and the 'policy' as well as the
'events' files.
In addition, there are 'buffer_size' and 'buffer_size_limit' that define
the initial and the upper limit of the size of a trace buffer.
A ready-to-use run script can by found in 'ports/run/noux_trace_fs.run'.