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Fix typo introduced with last commit. Also update TODO list.

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This commit is contained in:
Gregory Nutt 2017-10-11 10:25:27 -06:00
parent a00d8e16a1
commit 687aace769
2 changed files with 4 additions and 50 deletions
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50
TODO
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@ -1,4 +1,4 @@
NuttX TODO List (Last updated October 10, 2017)
NuttX TODO List (Last updated October 11, 2017)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This file summarizes known NuttX bugs, limitations, inconsistencies with
@ -22,7 +22,7 @@ nuttx/:
(16) Network (net/, drivers/net)
(4) USB (drivers/usbdev, drivers/usbhost)
(0) Other drivers (drivers/)
(14) Libraries (libc/, libm/)
(12) Libraries (libc/, libm/)
(10) File system/Generic drivers (fs/, drivers/)
(10) Graphics Subsystem (graphics/)
(3) Build system / Toolchains
@ -1740,52 +1740,6 @@ o Libraries (libc/, libm/)
Status: Open
Priority: Low
Title: printf()/flush() Cancellation Point Problems
Description: printf() calls flush() which, in turn calls write(). write()
is a cancellation point and both print() and flush() are
permitted to be cancellation points according to
OpenGroup.org.
However, calling write(), albeit indirectly from printf()
does not make it a "well behaved" cancellation point. When
write() exists, then the task or thread may be terminated
and printf() will leave the library semeaphore locked,
causing hang for the next task that calls printf().
There are basically three problems here. Resolution of
any of these problems:
1. It is optional if printf is a cancellation point. Because
it calls write() (indirectly), it is essentially a
cancellation point. But it could be possible to generate
a special interface, say nx_write() that behaves like
write() but is not a cancellation point. This function
would have to be accessible from user space for the
PROTECTED and KERNEL build.
2. pthreads maintain of list of all mutexes that they hold.
These are handling according to OpenGroup.org when the
pthread exits holding the mutex. There is nothing
comparable for tasks and semaphores, there is no list of
semaphores held for each tasks or pthreads and there is
no logic to deal with semaphores held when the task or
pthread exits.
3. NuttX supports nested cancellation points: A function
that is a cancellation point can call another function
that is also a cancellation point. The cancellation will
not occur until the final nested cancellation point
exits. So in the case of printf, if it were to be a
cancellation point, then the actual action exit would not
occur until printf() frees all semaphores and exits.
Unfortunately, printf() is a user space interface and the
cancellation interfaces are internal to the OS and would
not be available to printf() in the PROTECTED or KERNEL
build modes.
Status: Open
Priority: Medium-high. Anything that can result in a hang is
automatically pretty high priority.
o File system / Generic drivers (fs/, drivers/)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

4
include/nuttx/fs/fs.h
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@ -83,12 +83,12 @@
*/
#if defined(CONFIG_BUILD_FLAT) || defined(__KERNEL__)
# define _NX_WRITE(f,b,s) nx_write(s,b,s)
# define _NX_WRITE(f,b,s) nx_write(f,b,s)
# define _NX_GETERRNO(r) (-(r))
# define _NX_SETERRNO(r) set_errno(-(r))
# define _NX_GETERRVAL(r) (r)
#else
# define _NX_WRITE(f,b,s) write(s,b,s)
# define _NX_WRITE(f,b,s) write(f,b,s)
# define _NX_GETERRNO(r) errno
# define _NX_SETERRNO(r)
# define _NX_GETERRVAL(r) (-errno)