Upate README
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Gregory Nutt
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@ -230,19 +230,12 @@ SMP
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the emulation of multiple CPUs by creating multiple pthreads, each run a
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copy of the simulation in the same process address space.
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The simulation SMP implemention is incomplete, however. Two critical SMP
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functions are not implemented:
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At present, the SMP simulation is not fully functional: It does operate
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on the simulated CPU threads for a few context switches then fails during
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a setjmp() operation. I suspect that this is not an issue with the NuttX
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SMP logic but more likely some chaos in the pthread controls.
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- int up_cpu_pause(void)
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- int up_cpu_resume(void)
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These are used to start a new task on a different CPU: (1) the other CPU
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is stopped or paused, (2) the OS datastructures for that CPU are modified,
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then (2) the other CPU is resumed. Unfortunately, I have not yet thought
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of a way to implement them in the simulation.
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Currently, for example, you can enable SMP for ostest configuration by
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enabling:
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You can enable SMP for ostest configuration by enabling:
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-# CONFIG_EXPERIMENTAL is not set
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+CONFIG_EXPERIMENTAL=y
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@ -266,72 +259,18 @@ SMP
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-# CONFIG_SCHED_INSTRUMENTATION is not set
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+CONFIG_SCHED_INSTRUMENTATION=y
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The result should be as follows:
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The NSH configuration can also be forced to run SMP, but suffers from
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the same quirky behavior. I can be made reliable if you modify
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arch/sim/src/up_idle.c so that the IDLE loop only runs for CPU0.
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Otherwise, often simuart_post() will be called from CPU1 and it will
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try to restart NSH on CPU0 and, again, the same quirkiness occurs.
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- CPU0 initializes and starts CPU1. CPU1 is running an executing the
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IDLE task.
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But for example, this command:
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os_start: Entry
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os_idletask: CPU1: Beginning Idle Loop
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nsh> sleep 1 &
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- CPU0 brings up the the OS test application on CPU0
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os_do_appstart: Starting init thread
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CPU0: Start init, TCB@42f490, state=5
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up_unblock_task: Unblocking TCB=42f490
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CPU0: Suspend CPU0 IDLE, TCB@42c180, state=4
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CPU0: Resume init, TCB@42f490, state=0
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up_unblock_task: New Active Task TCB=42f490
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- OS test runs and performs some basic checks.
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stdio_test: write fd=1
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stdio_test: Standard I/O Check: printf
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stdio_test: write fd=2
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stdio_test: Standard I/O Check: fprintf to stderr
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ostest_main: putenv(Variable1=BadValue3)
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up_block_task: Blocking TCB=42f490
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CPU0: Suspend init, TCB@42f490, state=4
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CPU0: Resume CPU0 IDLE, TCB@42c180, state=3
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up_block_task: New Active Task TCB=42c180
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up_unblock_task: Unblocking TCB=42f490
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CPU0: Suspend CPU0 IDLE, TCB@42c180, state=4
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CPU0: Resume init, TCB@42f490, state=0
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up_unblock_task: New Active Task TCB=42f490
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ostest_main: setenv(Variable1, GoodValue1, TRUE)
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ostest_main: setenv(Variable2, BadValue1, FALSE)
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ostest_main: setenv(Variable2, GoodValue2, TRUE)
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ostest_main: setenv(Variable3, Variable3, FALSE)
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ostest_main: setenv(Variable3, Variable3, FALSE)
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show_variable: Variable=Variable1 has value=GoodValue1
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show_variable: Variable=Variable2 has value=GoodValue2
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show_variable: Variable=Variable3 has value=GoodValue3
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- Then OS test tries to start the task ostest on CPU1
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CPU0: Start ostest, TCB@430e90, state=5
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up_unblock_task: Unblocking TCB=430e90
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CPU1: Suspend CPU1 IDLE, TCB@42c2c0, state=4
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CPU0: Resume ostest, TCB@430e90, state=0
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ostest_main: Started user_main at PID=4
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There is no failure but, of course, the task on CPU1 does not run, i.e.,
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it does not replace the IDLE task running on CPU1.
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2016-02-16: The NSH configuration can be forced to run, but only if (1)
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You don't try to execute built-in commands or to execute commands in the
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background. Those thoses cases, it will try to start the command on
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CPU1 and the same problem as for the ostest case occurs.
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Also, for NSH you have to modify arch/sim/src/up_idle.c so that the
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IDLE loop only runfs for CPU0. Otherwise, often simuart_post() will
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be called from CPU1 and it will try to restart NSH on CPU0 and, again,
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the same problem occurs.
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2016-02-18: There is an initial implementation based on signals and
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signal handling, but this is not yet functional.
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will execute the sleep command on CPU1 which has worked every time
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that I have tried it (which is not too many times).
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BASIC
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^^^^^
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@ -942,12 +881,12 @@ unionfs
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afile.txt
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offset/
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When unionfs was created, file system was joined with and offset called
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When unionfs was created, file system was joined with and offset called
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offset". Therefore, all of the file system 2 root contents will appear
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to reside under a directory called offset/ (although there is no
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directory called offset/ on file system 2). Fie system 1 on the other
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hand does have an actual directory called offset/. If we list the
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contents of the offset/ directory in the unified file system, we see
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contents of the offset/ directory in the unified file system, we see
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he merged content of the file system 1 offset/ directory and the file
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system 2 root directory:
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