From: Vaibhav Jain vaibhav@linux.ibm.com
[ Upstream commit a5d6a3e73acbd619dd5b7b831762b755f9e2db80 ]
While removing large number of mappings from hash page tables for large memory systems as soft-lockup is reported because of the time spent inside htap_remove_mapping() like one below:
watchdog: BUG: soft lockup - CPU#8 stuck for 23s! <snip> NIP plpar_hcall+0x38/0x58 LR pSeries_lpar_hpte_invalidate+0x68/0xb0 Call Trace: 0x1fffffffffff000 (unreliable) pSeries_lpar_hpte_removebolted+0x9c/0x230 hash__remove_section_mapping+0xec/0x1c0 remove_section_mapping+0x28/0x3c arch_remove_memory+0xfc/0x150 devm_memremap_pages_release+0x180/0x2f0 devm_action_release+0x30/0x50 release_nodes+0x28c/0x300 device_release_driver_internal+0x16c/0x280 unbind_store+0x124/0x170 drv_attr_store+0x44/0x60 sysfs_kf_write+0x64/0x90 kernfs_fop_write+0x1b0/0x290 __vfs_write+0x3c/0x70 vfs_write+0xd4/0x270 ksys_write+0xdc/0x130 system_call+0x5c/0x70
Fix this by adding a cond_resched() to the loop in htap_remove_mapping() that issues hcall to remove hpte mapping. The call to cond_resched() is issued every HZ jiffies which should prevent the soft-lockup from being reported.
Suggested-by: Aneesh Kumar K.V aneesh.kumar@linux.ibm.com Signed-off-by: Vaibhav Jain vaibhav@linux.ibm.com Reviewed-by: Christophe Leroy christophe.leroy@csgroup.eu Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/20210404163148.321346-1-vaibhav@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/mm/book3s64/hash_utils.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/mm/book3s64/hash_utils.c b/arch/powerpc/mm/book3s64/hash_utils.c index 581b20a2feaf..286e7e8cb919 100644 --- a/arch/powerpc/mm/book3s64/hash_utils.c +++ b/arch/powerpc/mm/book3s64/hash_utils.c @@ -338,7 +338,7 @@ int htab_bolt_mapping(unsigned long vstart, unsigned long vend, int htab_remove_mapping(unsigned long vstart, unsigned long vend, int psize, int ssize) { - unsigned long vaddr; + unsigned long vaddr, time_limit; unsigned int step, shift; int rc; int ret = 0; @@ -351,8 +351,19 @@ int htab_remove_mapping(unsigned long vstart, unsigned long vend,
/* Unmap the full range specificied */ vaddr = ALIGN_DOWN(vstart, step); + time_limit = jiffies + HZ; + for (;vaddr < vend; vaddr += step) { rc = mmu_hash_ops.hpte_removebolted(vaddr, psize, ssize); + + /* + * For large number of mappings introduce a cond_resched() + * to prevent softlockup warnings. + */ + if (time_after(jiffies, time_limit)) { + cond_resched(); + time_limit = jiffies + HZ; + } if (rc == -ENOENT) { ret = -ENOENT; continue;