Messages in this thread |  | | Date | Mon, 20 Jul 2015 10:38:47 +0200 | | From | Ingo Molnar <> | | Subject | Re: [PATCH] sched, s390: Fix the fallout of increasing the offset of 'thread_struct' within 'task_struct' |
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* Martin Schwidefsky <schwidefsky@de.ibm.com> wrote:
> diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S > index 3238893..84062e7 100644 > --- a/arch/s390/kernel/entry.S > +++ b/arch/s390/kernel/entry.S > @@ -178,17 +178,21 @@ _PIF_WORK = (_PIF_PER_TRAP) > */ > ENTRY(__switch_to) > stmg %r6,%r15,__SF_GPRS(%r15) # store gprs of prev task > - stg %r15,__THREAD_ksp(%r2) # store kernel stack of prev > - lg %r4,__THREAD_info(%r2) # get thread_info of prev > - lg %r5,__THREAD_info(%r3) # get thread_info of next > + lgr %r1,%r2 > + aghi %r1,__TASK_thread # thread_struct of prev task > + lg %r4,__TASK_thread_info(%r2) # get thread_info of prev > + lg %r5,__TASK_thread_info(%r3) # get thread_info of next > + stg %r15,__THREAD_ksp(%r1) # store kernel stack of prev > + lgr %r1,%r3 > + aghi %r1,__TASK_thread # thread_struct of next task > lgr %r15,%r5 > aghi %r15,STACK_INIT # end of kernel stack of next > stg %r3,__LC_CURRENT # store task struct of next > stg %r5,__LC_THREAD_INFO # store thread info of next > stg %r15,__LC_KERNEL_STACK # store end of kernel stack > + lg %r15,__THREAD_ksp(%r1) # load kernel stack of next > lctl %c4,%c4,__TASK_pid(%r3) # load pid to control reg. 4 > mvc __LC_CURRENT_PID+4(4,%r0),__TASK_pid(%r3) # store pid of next > - lg %r15,__THREAD_ksp(%r3) # load kernel stack of next > lmg %r6,%r15,__SF_GPRS(%r15) # load gprs of next task > br %r14
Btw., I think we'd be slightly better off with the variant I sent: that way the offset arithmetics are done in C code and are ready in the relevant registers by the time they are used in __switch_to().
> > @@ -417,6 +421,7 @@ ENTRY(pgm_check_handler) > LAST_BREAK %r14 > lg %r15,__LC_KERNEL_STACK > lg %r14,__TI_task(%r12) > + aghi %r14,__TASK_thread # pointer to thread_struct > lghi %r13,__LC_PGM_TDB > tm __LC_PGM_ILC+2,0x02 # check for transaction abort > jz 2f
Don't we also need the chunk I have:
@@ -448,6 +449,7 @@ ENTRY(pgm_check_handler) nill %r10,0x007f sll %r10,2 je .Lsysc_return + ahi %r14,-__TASK_thread_struct # r14 now points to 'current' lgf %r1,0(%r10,%r1) # load address of handler routine lgr %r2,%r11 # pass pointer to pt_regs basr %r14,%r1 # branch to interrupt-handler
Because the 'basr' line relies on 'r14' having task_struct, I think?
But I don't really know what I'm talking about here ...
Thanks,
Ingo
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