Pull request partial deadlock fix #3
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The tick duration in microseconds may be calculated to zero depending on the processor clock speed. This patch sets it to 1 if the value is 0. Signed-off-by: Vinicius Tinti <[email protected]>
Map all OSAL internal types to common types already defined in <stdint.h>. Also adding support for x86_64. Signed-off-by: Vinicius Tinti <[email protected]>
The OSAL api uses a global lock to perform some operations using mutex,
semaphores, queues and so. This leads to a possible deadlock in the program
due the following situation.
Let "I" be the timer interrupt (SIG63):
|[Thread 1]
| ...
| call OS_TaskGetInfo
| ...
| lock(global)
| ...
I----+--------------------+
|[Interrupt]
| ...
| call OS_TaskGetInfo
| ...
| lock(global) // DEADLOCK
There are some possible solutions to avoid this problem. One is to never use any
OSAL primitives on the interrupt context, which quite limit the library. Other
would be block all signals during the global lock and let them be pending. This
approach may introduce poor performance. Other would be find out how to remove
these global locks. Another could be use safe locks on interrupt handler.
This patch implements the blocking signals solution because it is the best
trade-off of the current solutions.
There is also a single special case which is not handled by this patch.
Signed-off-by: Vinicius Tinti <[email protected]>
Signed-off-by: Vinicius Tinti <[email protected]>
Signed-off-by: Vinicius Tinti <[email protected]>
|
OSAL primitives in general are not intended to be interrupt safe. Feel free to implement and open source interrupt safe versions if you'd like, but not planning to overhaul the framework OSAL examples. |
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The OSAL api uses a global lock to perform some operations using mutex,
semaphores, queues and so. This leads to a possible deadlock in the program
due the following situation.
Let "I" be the timer interrupt (SIG63):
There are some possible solutions to avoid this problem. One is to never use any
OSAL primitives on the interrupt context, which quite limit the library. Other
would be block all signals during the global lock and let them be pending. This
approach may introduce poor performance. Other would be find out how to remove
these global locks. Another could be use safe locks on interrupt handler.
This patch implements the blocking signals solution because it is the best
trade-off of the current solutions.