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powerpc: Fix deadlock with multiple calls to smp_send_stop 

smp_send_stop can lock up the IPI path for any subsequent calls,
because the receiving CPUs spin in their handler function. This
started becoming a problem with the addition of an smp_send_stop
call in the reboot path, because panics can reboot after doing
their own smp_send_stop.

The NMI IPI variant was fixed with ac61c11566 ("powerpc: Fix
smp_send_stop NMI IPI handling"), which leaves the smp_call_function
variant.

This is fixed by having smp_send_stop only ever do the
smp_call_function once. This is a bit less robust than the NMI IPI
fix, because any other call to smp_call_function after smp_send_stop
could deadlock, but that has always been the case, and it was not
been a problem before.

Fixes: f2748bdfe1 ("powerpc/powernv: Always stop secondaries before reboot/shutdown")
Reported-by: Abdul Haleem <abdhalee@linux.vnet.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Nicholas Piggin 2018-04-27 11:51:59 +10:00 committed by Michael Ellerman
parent c0f7f5b6c6
commit 6029755eed
1 changed files with 43 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

63
arch/powerpc/kernel/smp.c
View File

@ -565,6 +565,35 @@ void crash_send_ipi(void (*crash_ipi_callback)(struct pt_regs *))
}
#endif
#ifdef CONFIG_NMI_IPI
static void nmi_stop_this_cpu(struct pt_regs *regs)
{
/*
* This is a special case because it never returns, so the NMI IPI
* handling would never mark it as done, which makes any later
* smp_send_nmi_ipi() call spin forever. Mark it done now.
*
* IRQs are already hard disabled by the smp_handle_nmi_ipi.
*/
nmi_ipi_lock();
nmi_ipi_busy_count--;
nmi_ipi_unlock();
/* Remove this CPU */
set_cpu_online(smp_processor_id(), false);
spin_begin();
while (1)
spin_cpu_relax();
}
void smp_send_stop(void)
{
smp_send_nmi_ipi(NMI_IPI_ALL_OTHERS, nmi_stop_this_cpu, 1000000);
}
#else /* CONFIG_NMI_IPI */
static void stop_this_cpu(void *dummy)
{
/* Remove this CPU */
@ -576,30 +605,24 @@ static void stop_this_cpu(void *dummy)
spin_cpu_relax();
}
#ifdef CONFIG_NMI_IPI
static void nmi_stop_this_cpu(struct pt_regs *regs)
{
/*
* This is a special case because it never returns, so the NMI IPI
* handling would never mark it as done, which makes any later
* smp_send_nmi_ipi() call spin forever. Mark it done now.
*/
nmi_ipi_lock();
nmi_ipi_busy_count--;
nmi_ipi_unlock();
stop_this_cpu(NULL);
}
#endif
void smp_send_stop(void)
{
#ifdef CONFIG_NMI_IPI
smp_send_nmi_ipi(NMI_IPI_ALL_OTHERS, nmi_stop_this_cpu, 1000000);
#else
static bool stopped = false;
/*
* Prevent waiting on csd lock from a previous smp_send_stop.
* This is racy, but in general callers try to do the right
* thing and only fire off one smp_send_stop (e.g., see
* kernel/panic.c)
*/
if (stopped)
return;
stopped = true;
smp_call_function(stop_this_cpu, NULL, 0);
#endif
}
#endif /* CONFIG_NMI_IPI */
struct thread_info *current_set[NR_CPUS];