Messages in this thread | | | Subject | Re: [PATCH 1/1] ppc/crash: Skip spinlocks during crash | From | Leonardo Bras <> | Date | Thu, 26 Mar 2020 20:26:59 -0300 |
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oops, forgot to EXPORT_SYMBOL. arch_spin_lock*() is used on modules.
Sending v2.
On Thu, 2020-03-26 at 19:28 -0300, Leonardo Bras wrote: > During a crash, there is chance that the cpus that handle the NMI IPI > are holding a spin_lock. If this spin_lock is needed by crashing_cpu it > will cause a deadlock. (rtas_lock and printk logbuf_log as of today) > > This is a problem if the system has kdump set up, given if it crashes > for any reason kdump may not be saved for crash analysis. > > Skip spinlocks after NMI IPI is sent to all other cpus. > > Signed-off-by: Leonardo Bras <leonardo@linux.ibm.com> > --- > arch/powerpc/include/asm/spinlock.h | 6 ++++++ > arch/powerpc/kexec/crash.c | 3 +++ > 2 files changed, 9 insertions(+) > > diff --git a/arch/powerpc/include/asm/spinlock.h b/arch/powerpc/include/asm/spinlock.h > index 860228e917dc..a6381d110795 100644 > --- a/arch/powerpc/include/asm/spinlock.h > +++ b/arch/powerpc/include/asm/spinlock.h > @@ -111,6 +111,8 @@ static inline void splpar_spin_yield(arch_spinlock_t *lock) {}; > static inline void splpar_rw_yield(arch_rwlock_t *lock) {}; > #endif > > +extern bool crash_skip_spinlock __read_mostly; > + > static inline bool is_shared_processor(void) > { > #ifdef CONFIG_PPC_SPLPAR > @@ -142,6 +144,8 @@ static inline void arch_spin_lock(arch_spinlock_t *lock) > if (likely(__arch_spin_trylock(lock) == 0)) > break; > do { > + if (unlikely(crash_skip_spinlock)) > + return; > HMT_low(); > if (is_shared_processor()) > splpar_spin_yield(lock); > @@ -161,6 +165,8 @@ void arch_spin_lock_flags(arch_spinlock_t *lock, unsigned long flags) > local_save_flags(flags_dis); > local_irq_restore(flags); > do { > + if (unlikely(crash_skip_spinlock)) > + return; > HMT_low(); > if (is_shared_processor()) > splpar_spin_yield(lock); > diff --git a/arch/powerpc/kexec/crash.c b/arch/powerpc/kexec/crash.c > index d488311efab1..8a522380027d 100644 > --- a/arch/powerpc/kexec/crash.c > +++ b/arch/powerpc/kexec/crash.c > @@ -66,6 +66,8 @@ static int handle_fault(struct pt_regs *regs) > > #ifdef CONFIG_SMP > > +bool crash_skip_spinlock; > + > static atomic_t cpus_in_crash; > void crash_ipi_callback(struct pt_regs *regs) > { > @@ -129,6 +131,7 @@ static void crash_kexec_prepare_cpus(int cpu) > /* Would it be better to replace the trap vector here? */ > > if (atomic_read(&cpus_in_crash) >= ncpus) { > + crash_skip_spinlock = true; > printk(KERN_EMERG "IPI complete\n"); > return; > } [unhandled content-type:application/pgp-signature] | |