Tiejun Chen wrote: > In entry_64.S version of ret_from_except_lite, you'll notice that > in the !preempt case, after we've checked MSR_PR we test for any > TIF flag in _TIF_USER_WORK_MASK to decide whether to go to do_work > or not. However, in the preempt case, we do a convoluted trick to > test SIGPENDING only if PR was set and always test NEED_RESCHED ... > but we forget to test any other bit of _TIF_USER_WORK_MASK !!! So > that means that with preempt, we completely fail to test for things > like single step, syscall tracing, etc... > > This should be fixed as the following path: > > - Test PR. If set, go to test_work_user, else continue. > > - In test_work_user, always test for _TIF_USER_WORK_MASK to decide to > go to do_work, maybe call it do_user_work > > - In test_work_kernel, test for _TIF_KERNEL_WORK_MASK which is set to > our new flag along with NEED_RESCHED if preempt is enabled and branch to > do_kernel_work.
Ben, Any comment for this? Tiejun > > Signed-off-by: Benjamin Herrenschmidt <b...@kernel.crashing.org> > Signed-off-by: Tiejun Chen <tiejun.c...@windriver.com> > --- > arch/powerpc/kernel/entry_64.S | 33 +++++++++++++++------------------ > 1 files changed, 15 insertions(+), 18 deletions(-) > > diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S > index d834425..9e70b9a 100644 > --- a/arch/powerpc/kernel/entry_64.S > +++ b/arch/powerpc/kernel/entry_64.S > @@ -571,27 +571,26 @@ _GLOBAL(ret_from_except_lite) > mtmsrd r9,1 /* Update machine state */ > #endif /* CONFIG_PPC_BOOK3E */ > > -#ifdef CONFIG_PREEMPT > - clrrdi r9,r1,THREAD_SHIFT /* current_thread_info() */ > - li r0,_TIF_NEED_RESCHED /* bits to check */ > - ld r3,_MSR(r1) > - ld r4,TI_FLAGS(r9) > - /* Move MSR_PR bit in r3 to _TIF_SIGPENDING position in r0 */ > - rlwimi r0,r3,32+TIF_SIGPENDING-MSR_PR_LG,_TIF_SIGPENDING > - and. r0,r4,r0 /* check NEED_RESCHED and maybe SIGPENDING */ > - bne do_work > - > -#else /* !CONFIG_PREEMPT */ > ld r3,_MSR(r1) /* Returning to user mode? */ > andi. r3,r3,MSR_PR > - beq restore /* if not, just restore regs and return */ > + bne test_work_user > > + clrrdi r9,r1,THREAD_SHIFT /* current_thread_info() */ > + li r0,_TIF_USER_WORK_MASK > +#ifdef CONFIG_PREEMPT > + ori r0,r0,_TIF_NEED_RESCHED > +#endif > + ld r4,TI_FLAGS(r9) > + and. r0,r4,r0 /* check NEED_RESCHED and maybe > _TIF_USER_WORK_MASK */ > + bne do_kernel_work > + b restore /* if so, just restore regs and return */ > + > +test_work_user: > /* Check current_thread_info()->flags */ > clrrdi r9,r1,THREAD_SHIFT > ld r4,TI_FLAGS(r9) > andi. r0,r4,_TIF_USER_WORK_MASK > - bne do_work > -#endif > + bne do_user_work > > restore: > BEGIN_FW_FTR_SECTION > @@ -693,10 +692,8 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS) > b .ret_from_except_lite /* loop back and handle more */ > #endif > > -do_work: > +do_kernel_work: > #ifdef CONFIG_PREEMPT > - andi. r0,r3,MSR_PR /* Returning to user mode? */ > - bne user_work > /* Check that preempt_count() == 0 and interrupts are enabled */ > lwz r8,TI_PREEMPT(r9) > cmpwi cr1,r8,0 > @@ -738,9 +735,9 @@ do_work: > bne 1b > b restore > > -user_work: > #endif /* CONFIG_PREEMPT */ > > +do_user_work: > /* Enable interrupts */ > #ifdef CONFIG_PPC_BOOK3E > wrteei 1 _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
