I don't understand why you need to do that.But for the SMP case there is a
better, lighter weight critical section called spinlock_irqsave. It is
intended to protect very short code sequences with a spin lock. Very
efficient.enter_critical_section is a big, fat pig in SMP and the lighter
spinlock should be used instead.The only thing is that the protected code
segment must not suspend itself while holding the spinlock.GregSent from
Samsung tablet.
-------- Original message --------From: "Nakamura, Yuuichi (Sony)"
<yuuichi.a.nakam...@sony.com> Date: 5/11/20 10:34 PM (GMT-06:00) To:
dev@nuttx.apache.org Cc: "Nakamura, Yuuichi (Sony)"
<yuuichi.a.nakam...@sony.com> Subject: RE: enter/leave_critical_section() calls
in the user space library Thanks for accepting my PR.Now it's ok for protected
build with uniprocessor case, but not sufficient in SMP case.The following
files included in the user mode library contain enter/leave_critical_section()
only when CONFIG_SMP=y.libs/libc/misc/lib_filesem.cmm/mm_heap/mm_sem.cThese may
have to be moved into the kernel space.Thanks,Yuuichi Nakamura> -----Original
Message-----> From: Xiang Xiao <xiaoxiang781...@gmail.com>> Sent: Monday, May
11, 2020 3:20 PM> To: dev@nuttx.apache.org> Subject: RE:
enter/leave_critical_section() calls in the user space library> > But we need
to consider syslog call from interrupt context too. So I think the> simple
modification is:> 1.Drop the critical section> 2.Keep the global variable> In
FLAT/PROTECTED build, all user space applications have to share the same>
variable.> > -----Original Message-----> From: Gregory Nutt
<spudan...@gmail.com>> Sent: Monday, May 11, 2020 12:35 PM> To:
dev@nuttx.apache.org> Subject: Re: enter/leave_critical_section() calls in the
user space library> > > > From this link:> >
https://linux.die.net/man/3/setlogmask> > logmask has per task scope not per
thread scope. So we still suffer the> concurrent issue if we change to
group-specific logmask.> > The same text appears in the more authoritative
Opengroup.org web page:>
https://pubs.opengroup.org/onlinepubs/7908799/xsh/closelog.html> > We meet that
requirement in the KERNEL mode, but not in the FLAT or> PROTECTED modes.> > So
the logmask must be in the group structure and setlogmask must become a> system
call at least in the FLAT and PROTECTED build. In the KERNEL build,> a plain
global variable as it is now is just fine. There will be one instance of the>
global variable in each process address space.> > pthread APIs are not
appropriate for use across processes (groups), so we> must avoid pthread
mutexes. This will not work in the KERNEL build mode> because each mutex lies
in a different address space. A usable mutex would> have to use something
like sem_open() which creates a semaphore can be> used across process
boundaries.> > Note that setlogmask is classified as NOT thread safe:
Preliminary: |> MT-Unsafe race:LogMask | AS-Unsafe | AC-Safe | See POSIX Safety
Concepts> <https://www.gnu.org/software/libc/manual/html_node/POSIX-Safety-Con>
cepts.html#POSIX-Safety-Concepts>.> See
https://www.gnu.org/software/libc/manual/html_node/setlogmask.html> > So we
should have no concern about thread safety. No re-entrancy protection> is
required. We can just remove the critical section. We do not need to use a>
semaphore or mutex.> > Greg>
