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Regard whitespace Rev 3295 → Rev 3296

/kernel/trunk/core/sys32.inc
707,3 → 707,78
; mov esi,boot_sched_2
; call boot_log
; ret
 
; Three following procedures are used to guarantee that
; some part of kernel code will not be terminated from outside
; while it is running.
; Note: they do not protect a thread from terminating due to errors inside
; the thread; accessing a nonexisting memory would still terminate it.
 
; First two procedures must be used in pair by thread-to-be-protected
; to signal the beginning and the end of an important part.
; It is OK to have nested areas.
 
; The last procedure must be used by outside wanna-be-terminators;
; if it is safe to terminate the given thread immediately, it returns eax=1;
; otherwise, it returns eax=0 and notifies the target thread that it should
; terminate itself when leaving a critical area (the last critical area if
; they are nested).
 
; Implementation. Those procedures use one dword in APPDATA for the thread,
; APPDATA.terminate_protection.
; * The upper bit is 1 during normal operations and 0 when terminate is requested.
; * Other bits form a number = depth of critical regions,
; plus 1 if the upper bit is 1.
; * When this dword goes to zero, the thread should be destructed,
; and the procedure in which it happened becomes responsible for destruction.
 
; Enter critical area. Called by thread which wants to be protected.
proc protect_from_terminate
mov edx, [current_slot]
; Atomically increment depth of critical areas and get the old value.
mov eax, 1
lock xadd [edx+APPDATA.terminate_protection], eax
; If the old value was zero, somebody has started to terminate us,
; so we are destructing and cannot do anything protected.
; Otherwise, return to the caller.
test eax, eax
jz @f
ret
@@:
; Wait for somebody to finish us.
call change_task
jmp @b
endp
 
; Leave critical area. Called by thread which wants to be protected.
proc unprotect_from_terminate
mov edx, [current_slot]
; Atomically decrement depth of critical areas.
lock dec [edx+APPDATA.terminate_protection]
; If the result of decrement is zero, somebody has requested termination,
; but at that moment we were inside a critical area; terminate now.
jz sys_end
; Otherwise, return to the caller.
ret
endp
 
; Request termination of thread identified by edx = SLOT_BASE + slot*256.
; Called by anyone.
proc request_terminate
xor eax, eax ; set return value
; Atomically clear the upper bit. If it was already zero, then
; somebody has requested termination before us, so just exit.
lock btr [edx+APPDATA.terminate_protection], 31
jnc .unsafe
; Atomically decrement depth of critical areas.
lock dec [edx+APPDATA.terminate_protection]
; If the result of decrement is nonzero, the target thread is inside a
; critical area; leave termination to leaving that area.
jnz .unsafe
; Otherwise, it is safe to kill the target now and the caller is responsible
; for this. Return eax=1.
inc eax
.unsafe:
ret
endp