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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) - sys_prot_t sys_arch_protect(void)
This optional function does a "fast" critical region protection and returns This optional function does a "fast" critical region protection. This function
the previous protection level. This function is only called during very short is only called during very short critical regions. An embedded system which
critical regions. An embedded system which supports ISR-based drivers might supports ISR-based drivers might want to implement this function by disabling
want to implement this function by disabling interrupts. Task-based systems interrupts. Task-based systems might want to implement this by using a mutex
might want to implement this by using a mutex or disabling tasking. This or disabling tasking. This function should support recursive calls from the
function should support recursive calls from the same task or interrupt. In same task or interrupt. In other words, sys_arch_protect() could be called
other words, sys_arch_protect() could be called while already protected. In while already protected.
that case the return value indicates that it is 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 sys_arch_protect() is only required if your port is supporting an operating
system. system.
- void sys_arch_unprotect(sys_prot_t pval) - void sys_arch_unprotect(sys_prot_t pval)
This optional function does a "fast" set of critical region protection to the This optional function does a "fast" exit of critical region protection
value specified by pval. See the documentation for sys_arch_protect() for nesting level. The value passed in pval is the opaque value returned the
more information. This function is only required if your port is supporting respective call to sys_arch_protect(). See the documentation for
an operating system. 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: For some configurations, you also need: