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2008-07-10 Till Straumann <strauman@slac.stanford.edu>

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* new-exceptions/bspsupport/ppc_exc.S: must disable
	interrupts prior to restoring SRRs (thanks to Sebastian Huber)
This commit is contained in:
Till Straumann
2008-07-10 21:29:27 +00:00
parent 055173d46a
commit 38f5e616fc
1 changed files with 20 additions and 0 deletions
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20
c/src/lib/libcpu/powerpc/new-exceptions/bspsupport/ppc_exc.S
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@@ -271,6 +271,10 @@ skip_save_nonvolatile_regs:
/* decrement ISR nest level;
* disable all interrupts.
* (Disabling IRQs here is not necessary if we
* use the stack-switching strategy which tests
* if we are alreay on the ISR-stack as opposed
* to test the nesting level; see ppc_exc_asm_macros.h)
*/
lwz r4, ppc_exc_msr_irq_mask@sdarel(r13)
mfmsr r5
@@ -365,6 +369,22 @@ skip_restore_nonvolatile_regs:
lwz r4, EXC_CR_OFFSET(r1)
mtcr r4
/* Must disable interrupts prior to restoring SSRs.
* Here's a scenario discovered by Sebastian Huber:
* 1) CE happens between writing to SRR and RFI
* 2) CE handler does something which requires a task switch
* 3) CE wrapper returns and determines that task switch
* is OK since EE lock is not held, dispatch-disable level
* is zero etc.
* 4) switch to other task enables EE
* 5) eventually, switch back to task interrupted by 1)
* 6) RFI happens but SRR contents have been clobbered.
*/
lwz r4, ppc_exc_msr_irq_mask@sdarel(r13)
mfmsr r5
andc r4, r5, r4
mtmsr r4
/* restore SRR and stack */
lwz r4, SRR0_FRAME_OFFSET(r1)
lwz r5, SRR1_FRAME_OFFSET(r1)