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author | patacongo <patacongo@42af7a65-404d-4744-a932-0658087f49c3> | 2010-11-05 00:29:37 +0000 |
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committer | patacongo <patacongo@42af7a65-404d-4744-a932-0658087f49c3> | 2010-11-05 00:29:37 +0000 |
commit | 019a4a61f0173e09a532d47c0979367cae365d0c (patch) | |
tree | d2b416cca9851f4568b5583885a7791c4dbaa658 | |
parent | 56055db490d414f38d5ba6fc949279ae4fbc51ba (diff) | |
download | px4-nuttx-019a4a61f0173e09a532d47c0979367cae365d0c.tar.gz px4-nuttx-019a4a61f0173e09a532d47c0979367cae365d0c.tar.bz2 px4-nuttx-019a4a61f0173e09a532d47c0979367cae365d0c.zip |
Update some comments
git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@3073 42af7a65-404d-4744-a932-0658087f49c3
-rw-r--r-- | nuttx/arch/avr/include/avr32/irq.h | 1 | ||||
-rwxr-xr-x | nuttx/arch/avr/src/avr32/up_fullcontextrestore.S | 22 | ||||
-rw-r--r-- | nuttx/arch/avr/src/avr32/up_sigdeliver.c | 17 |
3 files changed, 37 insertions, 3 deletions
diff --git a/nuttx/arch/avr/include/avr32/irq.h b/nuttx/arch/avr/include/avr32/irq.h index caa6e9f5a..a9d0d8626 100644 --- a/nuttx/arch/avr/include/avr32/irq.h +++ b/nuttx/arch/avr/include/avr32/irq.h @@ -98,7 +98,6 @@ #define INTCONTEXT_REGS 8 /* r8-r12, lr, pc, sr */ #define XCPTCONTEXT_REGS 17 /* Plus r0-r7, sp */ - /**************************************************************************** * Public Types ****************************************************************************/ diff --git a/nuttx/arch/avr/src/avr32/up_fullcontextrestore.S b/nuttx/arch/avr/src/avr32/up_fullcontextrestore.S index c40239307..c883c58c7 100755 --- a/nuttx/arch/avr/src/avr32/up_fullcontextrestore.S +++ b/nuttx/arch/avr/src/avr32/up_fullcontextrestore.S @@ -53,6 +53,28 @@ /****************************************************************************
* Name: up_fullcontextrestore
*
+ * Descripion:
+ * Restore the full-running contex of a thread.
+ *
+ * NOTE: Thus function must handle one very strange case. That is when
+ * this function is called with up_sigdeliver(). That case is strange in
+ * two ways:
+ *
+ * 1. It is not a context switch between threads. Rather, up_fullcontextrestore
+ * must behave more it more like a longjmp within the same task, using the
+ * same stack.
+ * 2. In this case, this function is called with r12 pointing to a register
+ * save area on the stack to be destroyed. This is dangerous for two
+ * reasons: (a) there is a period of time where the stack contents still
+ * contain valid data, but are outside of range protected by the stack
+ * pointer (hence, interrupts must be disabled), and (b) there is the
+ * very real possibility that the new stack pointer might overlap with
+ * the register save area and stack usage in this function might corrupt
+ * the register save data before the state is restored.
+ *
+ * Input Parameters:
+ * r12 = A pointer to the register save area of the thread to be restored.
+ *
* C Prototype:
* void up_fullcontextrestore(uint32_t *regs);
*
diff --git a/nuttx/arch/avr/src/avr32/up_sigdeliver.c b/nuttx/arch/avr/src/avr32/up_sigdeliver.c index aa3940b79..b000f118a 100644 --- a/nuttx/arch/avr/src/avr32/up_sigdeliver.c +++ b/nuttx/arch/avr/src/avr32/up_sigdeliver.c @@ -82,7 +82,7 @@ void up_sigdeliver(void) { _TCB *rtcb = (_TCB*)g_readytorun.head; - uint32_t regs[XCPTCONTEXT_REGS]; + uint32_t regs[XCPTCONTEXT_REGS+3]; /* Why +3? See below */ sig_deliver_t sigdeliver; /* Save the errno. This must be preserved throughout the signal handling @@ -128,7 +128,20 @@ void up_sigdeliver(void) (void)irqsave(); rtcb->pterrno = saved_errno; - /* Then restore the correct state for this thread of execution. */ + /* Then restore the correct state for this thread of execution. This is an + * unusual case that must be handled by up_fullcontextresore. This case is + * unusal in two ways: + * + * 1. It is not a context switch between threads. Rather, up_fullcontextrestore + * must behave more it more like a longjmp within the same task, using + * he same stack. + * 2. In this case, up_fullcontextrestore is called with r12 pointing to + * a register save area on the stack to be destroyed. This is + * dangerous because there is the very real possibility that the new + * stack pointer might overlap with the register save area and hat stack + * usage in up_fullcontextrestore might corrupt the register save data + * before the state is restored. + */ up_ledoff(LED_SIGNAL); up_fullcontextrestore(regs); |