From: Nathan Lynch nathanl@linux.ibm.com
[ Upstream commit ccfb5bd71d3d1228090a8633800ae7cdf42a94ac ]
After a partition migration, pseries_devicetree_update() processes changes to the device tree communicated from the platform to Linux. This is a relatively heavyweight operation, with multiple device tree searches, memory allocations, and conversations with partition firmware.
There's a few levels of nested loops which are bounded only by decisions made by the platform, outside of Linux's control, and indeed we have seen RCU stalls on large systems while executing this call graph. Use cond_resched() in these loops so that the cpu is yielded when needed.
Signed-off-by: Nathan Lynch nathanl@linux.ibm.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/20190802192926.19277-4-nathanl@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/platforms/pseries/mobility.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/arch/powerpc/platforms/pseries/mobility.c b/arch/powerpc/platforms/pseries/mobility.c index 4addc552eb33d..9739a055e5f7b 100644 --- a/arch/powerpc/platforms/pseries/mobility.c +++ b/arch/powerpc/platforms/pseries/mobility.c @@ -12,6 +12,7 @@ #include <linux/cpu.h> #include <linux/kernel.h> #include <linux/kobject.h> +#include <linux/sched.h> #include <linux/smp.h> #include <linux/stat.h> #include <linux/completion.h> @@ -208,7 +209,11 @@ static int update_dt_node(__be32 phandle, s32 scope)
prop_data += vd; } + + cond_resched(); } + + cond_resched(); } while (rtas_rc == 1);
of_node_put(dn); @@ -317,8 +322,12 @@ int pseries_devicetree_update(s32 scope) add_dt_node(phandle, drc_index); break; } + + cond_resched(); } } + + cond_resched(); } while (rc == 1);
kfree(rtas_buf);