778a4a9dd4
happens, the context of the interrupted thread is exported to userland. Unlike most contexts, it will be an async context and we cannot easily use our existing functions to set such a context. To avoid a lot of complexity that may possibly interfere with the common case, we simply let the kernel deal with it. However, we don't use the EPC based syscall path to invoke setcontext(2). No, we use the break-based syscall path. That way the trapframe will be compatible with the context we're trying to restore and we save the kernel a lot of trouble. The kind of trouble we did not want to go though ourselves... However, we also need to set the threads mailbox and there's no syscall to help us out. To avoid creating a new syscall, we use the context itself to pass the information to the kernel so that the kernel can update the mailbox. This involves setting a flag (_MC_FLAGS_KSE_SET_MBOX) and setting ifa (the address) and isr (the value). |
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