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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 /nuttx/arch/avr/src/avr32/up_fullcontextrestore.S | |
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
Diffstat (limited to 'nuttx/arch/avr/src/avr32/up_fullcontextrestore.S')
-rwxr-xr-x | nuttx/arch/avr/src/avr32/up_fullcontextrestore.S | 22 |
1 files changed, 22 insertions, 0 deletions
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);
*
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