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author | Ralf Baechle <ralf@linux-mips.org> | 2007-03-29 23:42:42 +0100 |
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committer | Ralf Baechle <ralf@linux-mips.org> | 2007-03-29 23:46:36 +0100 |
commit | 8a1e97ee2e025f116765c92409a3cf8f6cb07ad6 (patch) | |
tree | c3df538fce3f32b35b1b8355a9a411cb668e724e /arch | |
parent | 6c9fde4bfff11b2fd93b4e518ae7ecb25a9244e4 (diff) | |
download | lwn-8a1e97ee2e025f116765c92409a3cf8f6cb07ad6.tar.gz lwn-8a1e97ee2e025f116765c92409a3cf8f6cb07ad6.zip |
[MIPS] SMTC: Fix recursion in instant IPI replay code.
local_irq_restore -> raw_local_irq_restore -> irq_restore_epilog ->
smtc_ipi_replay -> smtc_ipi_dq -> spin_unlock_irqrestore ->
_spin_unlock_irqrestore -> local_irq_restore
The recursion does abort when there is no more IPI queued for a CPU, so
this isn't usually fatal which is why we got away with this for so long
until this was discovered by code inspection.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Diffstat (limited to 'arch')
-rw-r--r-- | arch/mips/kernel/smtc.c | 40 |
1 files changed, 33 insertions, 7 deletions
diff --git a/arch/mips/kernel/smtc.c b/arch/mips/kernel/smtc.c index e50fe20571f0..5dcfab6b288e 100644 --- a/arch/mips/kernel/smtc.c +++ b/arch/mips/kernel/smtc.c @@ -999,10 +999,17 @@ static void setup_cross_vpe_interrupts(unsigned int nvpe) /* * SMTC-specific hacks invoked from elsewhere in the kernel. + * + * smtc_ipi_replay is called from raw_local_irq_restore which is only ever + * called with interrupts disabled. We do rely on interrupts being disabled + * here because using spin_lock_irqsave()/spin_unlock_irqrestore() would + * result in a recursive call to raw_local_irq_restore(). */ -void smtc_ipi_replay(void) +static void __smtc_ipi_replay(void) { + unsigned int cpu = smp_processor_id(); + /* * To the extent that we've ever turned interrupts off, * we may have accumulated deferred IPIs. This is subtle. @@ -1017,17 +1024,30 @@ void smtc_ipi_replay(void) * is clear, and we'll handle it as a real pseudo-interrupt * and not a pseudo-pseudo interrupt. */ - if (IPIQ[smp_processor_id()].depth > 0) { - struct smtc_ipi *pipi; - extern void self_ipi(struct smtc_ipi *); + if (IPIQ[cpu].depth > 0) { + while (1) { + struct smtc_ipi_q *q = &IPIQ[cpu]; + struct smtc_ipi *pipi; + extern void self_ipi(struct smtc_ipi *); + + spin_lock(&q->lock); + pipi = __smtc_ipi_dq(q); + spin_unlock(&q->lock); + if (!pipi) + break; - while ((pipi = smtc_ipi_dq(&IPIQ[smp_processor_id()]))) { self_ipi(pipi); - smtc_cpu_stats[smp_processor_id()].selfipis++; + smtc_cpu_stats[cpu].selfipis++; } } } +void smtc_ipi_replay(void) +{ + raw_local_irq_disable(); + __smtc_ipi_replay(); +} + EXPORT_SYMBOL(smtc_ipi_replay); void smtc_idle_loop_hook(void) @@ -1132,7 +1152,13 @@ void smtc_idle_loop_hook(void) * is in use, there should never be any. */ #ifndef CONFIG_MIPS_MT_SMTC_INSTANT_REPLAY - smtc_ipi_replay(); + { + unsigned long flags; + + local_irq_save(flags); + __smtc_ipi_replay(); + local_irq_restore(flags); + } #endif /* CONFIG_MIPS_MT_SMTC_INSTANT_REPLAY */ } |