Greetings:
The 2.4.19-pre3 works just dandy as it is without this patch,
but it is needed for O(1) scheduler. I think Martin was going
to forward this into 2.5.x tree, where O(1) is standard.
The problem is that schedule_tail() is supposed to unlock
runqueue, but if interrupts are enabled before that happens,
a timer tick may squeeze in and deadlock. I observed such
situation myself.
So, I would like this to be in 2.4.19 for the sake of O(1) users.
Any objections?
-- Pete
diff -ur -X dontdiff linux-2.4.19-pre3/arch/s390/kernel/entry.S linux-2.4.19-pre3-390/arch/s390/kernel/entry.S
--- linux-2.4.19-pre3/arch/s390/kernel/entry.S Tue Mar 12 10:53:36 2002
+++ linux-2.4.19-pre3-390/arch/s390/kernel/entry.S Fri Mar 15 09:18:52 2002
@@ -254,13 +254,14 @@
ret_from_fork:
basr %r13,0
l %r13,.Lentry_base-.(%r13) # setup base pointer to &entry_base
+ # not saving R14 here because we go to sysc_return ultimately
+ l %r1,BASED(.Lschedtail)
+ basr %r14,%r1 # call schedule_tail (unlock stuff)
GET_CURRENT # load pointer to task_struct to R9
stosm 24(%r15),0x03 # reenable interrupts
sr %r0,%r0 # child returns 0
st %r0,SP_R2(%r15) # store return value (change R2 on stack)
- l %r1,BASED(.Lschedtail)
- la %r14,BASED(sysc_return)
- br %r1 # call schedule_tail, return to sysc_return
+ b BASED(sysc_return)
#
# clone, fork, vfork, exec and sigreturn need glue,
diff -ur -X dontdiff linux-2.4.19-pre3/arch/s390x/kernel/entry.S linux-2.4.19-pre3-390/arch/s390x/kernel/entry.S
--- linux-2.4.19-pre3/arch/s390x/kernel/entry.S Tue Mar 12 10:53:36 2002
+++ linux-2.4.19-pre3-390/arch/s390x/kernel/entry.S Fri Mar 15 09:20:33 2002
@@ -240,11 +240,11 @@
#
.globl ret_from_fork
ret_from_fork:
+ brasl %r14,schedule_tail
GET_CURRENT # load pointer to task_struct to R9
stosm 48(%r15),0x03 # reenable interrupts
xc SP_R2(8,%r15),SP_R2(%r15) # child returns 0
- larl %r14,sysc_return
- jg schedule_tail # return to sysc_return
+ j sysc_return
#
# clone, fork, vfork, exec and sigreturn need glue,
-
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This archive was generated by hypermail 2b29 : Fri Mar 15 2002 - 22:00:21 EST