Adam Lackorzynski wrote:
Hi,
So I'm looking at the late v2 version of Fiasco and I'm reading the code such that ~0 means "don't change this value". The current/old value is delivered back in any case. Regarding the L4_INVALID_ID, I'm reading the code such that the pager will not be set when the target ID does not exist, which includes L4_INVALID_ID, i.e. the thread's pager should not be changed.
but strange that it got a pagefault in case ~0 or L4_INVALID_ID is specified, but does not change the registers or/and pager/preempter if I specify 0 for eip/esp or l4_threadid_t initialized with zeros instead of L4_INVALID_ID
So, is it possible anyhow to suspend/resume the running thread from another thread? I know, that the thread can be suspended if entering unconditional l4_ipc_wait(), but this is from the inside that thread. How could it be done from an outside thread?
One way is to set the thread on such a loop via ex_regs (and paying attention to the register contents which basically means there's some assembly code involved). Another way is to do ex_regs(id, ~0, ~0, L4_THREAD_EX_REGS_RAISE_EXCEPTION) which will trigger an artificial exception in the thread and have it send an exception IPC to its pager. The pager should then just not reply to have the thread suspended, and then reply when you want to have the thread go on later. What makes this a bit tricky is when L4 IPC is involves which you will cancel with ex_regs, or not, if you use the L4_THREAD_EX_REGS_NO_CANCEL flag.
I tried the 1st way -- set eip to the address of IPC wait loop, so it does suspend here, but resume doesn't work. -- You said that I'll need to set some registers via assember, but I wonder which ones -- the changed one is eip only. esp and eflags are only read, but didn't changed, others seems to be not altered with ex_regs...
Adam