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.c mm/mm_heap/mm_sem.c These 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 >
