events: Move implementation of events::send() to lib/events #499
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Events have a global, system-wide sequence number, which must be handled atomically, (fetching and incrementing the sequence AND sending the event to uORB must be atomic). Currently in FLAT mode, only one instance of this sequence number exists, so it is OK to have it in px4_platform. However, in PROTECTED mode px4_platform is instantiated both in kernel- and user spaces, which makes two instances of this sequence number, which causes problems in the mavlink event handling logic. When mavlink receives and handles events, it expects that: - The sequence numbers arrive in order (seq n is followed by n+1 etc) - It increments by 1 - There is only one instance of the sequence number In PROTECTED mode this is violated, as the kernel and user sequence numbers run freely on their own. This patch fixes the issue by moving the event backend to the kernel and by providing user access to it via ioctl.
jlaitine
approved these changes
Sep 21, 2023
|
I'll merge this for now as it fixes a bug for us. The upstream solution might necessitate some modifications but this commit can just be dropped/replaced when rebasing. |
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Events have a global, system-wide sequence number, which must be handled atomically, (fetching and incrementing the sequence AND sending the event to uORB must be atomic). Currently in FLAT mode, only one instance of this sequence number exists, so it is OK to have it in px4_platform.
However, in PROTECTED mode px4_platform is instantiated both in kernel- and user spaces, which makes two instances of this sequence number, which causes problems in the mavlink event handling logic.
When mavlink receives and handles events, it expects that:
In PROTECTED mode this is violated, as the kernel and user sequence numbers run freely on their own. This patch fixes the issue by moving the event backend to the kernel and by providing user access to it via ioctl.