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Clarify that sys_arch_protect() always has a matching unprotect.

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This is to allow an implementation to use a nesting counter, or a
recursive mutex. Also clarify that the value returned by
sys_arch_protect() is opaque to lwip and implementation dependent.

Signed-off-by: goldsimon <goldsimon@gmx.de>
This commit is contained in:
Our Air Quality 2017-07-20 22:21:34 +10:00 committed by goldsimon
parent d01b3177fd
commit 66a84cb2ef
1 changed files with 18 additions and 12 deletions
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30
doc/sys_arch.txt
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@ -214,24 +214,30 @@ main-loop and from interrupts), the SYS_LIGHTWEIGHT_PROT protection SHOULD be en
- sys_prot_t sys_arch_protect(void)
This optional function does a "fast" critical region protection and returns
the previous protection level. This function is only called during very short
critical regions. An embedded system which supports ISR-based drivers might
want to implement this function by disabling interrupts. Task-based systems
might want to implement this by using a mutex or disabling tasking. This
function should support recursive calls from the same task or interrupt. In
other words, sys_arch_protect() could be called while already protected. In
that case the return value indicates that it is already protected.
This optional function does a "fast" critical region protection. This function
is only called during very short critical regions. An embedded system which
supports ISR-based drivers might want to implement this function by disabling
interrupts. Task-based systems might want to implement this by using a mutex
or disabling tasking. This function should support recursive calls from the
same task or interrupt. In other words, sys_arch_protect() could be called
while already protected.
The return value is opaque to lwip and passed to the sys_arch_unprotect() call
matching the sys_arch_protect() call at the same nesting level. This value
might be used to restore the status. However implementations may depend on
every call to sys_arch_protect() having a matching call to sys_arch_unprotect()
and thus can use a nesting count or a recursive mutex.
sys_arch_protect() is only required if your port is supporting an operating
system.
- void sys_arch_unprotect(sys_prot_t pval)
This optional function does a "fast" set of critical region protection to the
value specified by pval. See the documentation for sys_arch_protect() for
more information. This function is only required if your port is supporting
an operating system.
This optional function does a "fast" exit of critical region protection
nesting level. The value passed in pval is the opaque value returned the
respective call to sys_arch_protect(). See the documentation for
sys_arch_protect() for more information. This function is only required if
your port is supporting an operating system.
For some configurations, you also need: