This was obsolete and broken based upon recent time keeping changes.
Thie build option was previously enabled by adding
USE_TICKS_FOR_STATISTICS=1 to the configure command line.
This propagated into the code as preprocessor conditionals
using the __RTEMS_USE_TICKS_FOR_STATISTICS__ conditional.
Add an assert to ensure that the watchdog is the proper state for a
_Watchdog_Initialize(). This helps to detect invalid initializations
which may lead to a corrupt watchdog chain.
This reverts commit 46ae1d7a2b.
The _Timecounter_Tick_simple() function actually doesn't switch to the
next timehand, so it is all right to use the simple timecounter approach
even on SMP configurations. The use of simple timecounters is not
recommended however since they impose a performance penalty.
When updating/accessing the timehands, barriers are needed to ensure
that:
- th_generation update is visible after the parameters update is
visible;
- the read of parameters is not reordered before initial read of
th_generation.
On UP kernels, compiler barriers are enough. For SMP machines, CPU
barriers must be used too, as was confirmed by submitter by testing on
the Freescale T4240 platform with 24 PowerPC processors.
Submitted by: Sebastian Huber <sebastian.huber@embedded-brains.de>
MFC after: 1 week
Implement a mechanism for making changes in the kernel<->driver PPS
interface without breaking ABI or API compatibility with existing drivers.
The existing data structures used to communicate between the kernel and
driver portions of PPS processing contain no spare/padding fields and no
flags field or other straightforward mechanism for communicating changes
in the structures or behaviors of the code. This makes it difficult to
MFC new features added to the PPS facility. ABI compatibility is
important; out-of-tree drivers in module form are known to exist. (Note
that the existing api_version field in the pps_params structure must
contain the value mandated by RFC 2783 and any RFCs that come along after.)
These changes introduce a pair of abi-version fields which are filled in
by the driver and the kernel respectively to indicate the interface
version. The driver sets its version field before calling the new
pps_init_abi() function. That lets the kernel know how much of the
pps_state structure is understood by the driver and it can avoid using
newer fields at the end of the structure that it knows about if the driver
is a lower version. The kernel fills in its version field during the init
call, letting the driver know what features and data the kernel supports.
To implement the new version information in a way that is backwards
compatible with code from before these changes, the high bit of the
lightly-used 'kcmode' field is repurposed as a flag bit that indicates the
driver is aware of the abi versioning scheme. Basically if this bit is
clear that indicates a "version 0" driver and if it is set the driver_abi
field indicates the version.
These changes also move the recently-added 'mtx' field of pps_state from
the middle to the end of the structure, and make the kernel code that uses
this field conditional on the driver being abi version 1 or higher. It
changes the only driver currently supplying the mtx field, usb_serial, to
use pps_init_abi().
Reviewed by: hselasky@
The SPARC ABI is a bit special with respect to the floating point context.
The complete floating point context is volatile. Thus from an ABI point
of view nothing needs to be saved and restored during a context switch.
Instead the floating point context must be saved and restored during
interrupt processing. Historically the deferred floating point switch is
used for SPARC and the complete floating point context is saved and
restored during a context switch to the new floating point unit owner.
This is a bit dangerous since post-switch actions (e.g. signal handlers)
and context switch extensions may silently corrupt the floating point
context. The floating point unit is disabled for interrupt handlers.
Thus in case an interrupt handler uses the floating point unit then this
will result in a trap.
On SMP configurations the deferred floating point switch is not
supported in principle. So use here a safe floating point support. Safe
means that the volatile floating point context is saved and restored
around a thread dispatch issued during interrupt processing. Thus
post-switch actions and context switch extensions may safely use the
floating point unit.
Update #2270.
Store the floating-point unit property in the thread control block
regardless of the CPU_HARDWARE_FP and CPU_SOFTWARE_FP settings. Make
sure the floating-point unit is only enabled for the corresponding
multilibs. This helps targets which have a volatile only floating point
context like SPARC for example.
Define CONTEXT_FP_SIZE to zero in case hardware and software floating
point support is disabled. The problem is that empty structures have a
different size in C and C++. In C++ they have a non-zero size leading
to an overestimate of the workspace size.
With the introduction of fine grained locking there is no longer a
one-to-one connection between the Giant lock nest level and the thread
dispatch disable level.
It is wrong to restore the floating point context here. The
_Context_Switch() ends up in _Thread_Handler() which will call
_Thread_Restore_fp(). In _Thread_Do_dispatch() the FP restore is after
the context switch.
In case the zlib compression was used, then the librtemscpu.a depended
on libz.a. To avoid a GCC patch or complicated link flags move the
JFFS2 support into a separate library to use a simple "-ljffs2 -lz" to
link the executable.
basic VGA driver can be enabled during configure phase by exporting variable
USE_VGA=1 so that it is available in configure environment
cirrus driver is enabled the same way by exporting variable
USE_CIRRUS_GD5446=1
driver is not initialized by default
initialization is possible through multiboot command line option or
through the string variable (see fb_default_mode.h) set in user's module
allowing the driver to evaluate this variable after the two
modules are linked together
