From 5e8549d200dbd88869ae856f007e37e3c2bd2c10 Mon Sep 17 00:00:00 2001 From: Thomas Petazzoni Date: Fri, 15 Jun 2018 17:52:37 +0200 Subject: [PATCH] arch/sh: use slow path for get_user_pages_fast() on SMP The fast path of get_user_pages_fast() disables IRQs and then does: - gup_pud_range() - gup_pmd_range() - gup_pte_range() - flush_dcache_page() However, flush_dcache_page() makes a smp_call_function(), and using smp_call_function() when IRQs are disabled is not allowed. In order to work around this problem, this commit prevents the fast path from get_user_pages_fast() from being used on SMP, and directly uses the slow path, which doesn't disable interrupts. Fixes the following warning when get_futex_key() is called: WARNING: CPU: 1 PID: 410 at kernel/smp.c:416 smp_call_function_many+0x1fc/0x2ac Modules linked in: CPU: 1 PID: 410 Comm: wdc-pfmu-test Tainted: G O 4.13.0-00035-g0d3023c733a0-dirty #363 task: 97d9a120 task.stack: 97d2e000 PC is at smp_call_function_many+0x1fc/0x2ac PR is at smp_call_function_many+0x1e2/0x2ac PC : 88071fd4 SP : 97d2fcd4 SR : 400080f1 TEA : c06d6840 R0 : 000000f0 R1 : 00000002 R2 : 00000000 R3 : 8849c89c R4 : 886d62c4 R5 : 886d62c4 R6 : 886db928 R7 : 884a9dec R8 : 00000000 R9 : ffffffff R10 : 8844667c R11 : 29ee9000 R12 : 8844667c R13 : 00000001 R14 : 97d2fcd4 MACH: 000177e7 MACL: 0000018c GBR : 295742d0 PR : 88071fba Call trace: [<8800fe2c>] sh4_flush_dcache_page+0x0/0xa4 [<880720a2>] smp_call_function+0x1e/0x50 [<8800fe2c>] sh4_flush_dcache_page+0x0/0xa4 [<8800ecc0>] flush_dcache_page+0x34/0x74 [<88010d1c>] gup_pte_range+0xd0/0x140 [<88010e04>] gup_pmd_range+0x78/0xa8 [<88010c4c>] gup_pte_range+0x0/0x140 [<88011006>] get_user_pages_fast+0xda/0x130 [<8806f376>] get_futex_key+0x72/0x3a0 [<8806f6a4>] futex_wait_setup+0x0/0x10c [<88055a08>] __rcu_read_unlock+0x0/0x54 [<880559c8>] __rcu_read_lock+0x0/0x1c [<88010f2c>] get_user_pages_fast+0x0/0x130 [<8806f6de>] futex_wait_setup+0x3a/0x10c [<8806f6a4>] futex_wait_setup+0x0/0x10c [<8806f852>] futex_wait+0xa2/0x1b8 [<8806f6a4>] futex_wait_setup+0x0/0x10c [<88071c00>] smp_call_function_single+0xac/0x108 [<8800e908>] cache_noop+0x0/0xc [<8800e908>] cache_noop+0x0/0xc [<88071018>] do_futex+0x108/0x8f8 [<880bdfe4>] finish_fault+0x38/0x70 [<880bdff2>] finish_fault+0x46/0x70 [<880bf212>] handle_mm_fault+0x2f6/0x954 [<880bf21a>] handle_mm_fault+0x2fe/0x954 [<88030e64>] resched_curr+0x54/0x6c [<8832be9e>] _raw_spin_lock_irqsave+0xa/0x18 [<880718dc>] SyS_futex+0xd4/0x124 [<8801488e>] SyS_clone+0x16/0x24 [<8800727e>] syscall_call+0x18/0x1e [<88071808>] SyS_futex+0x0/0x124 Signed-off-by: Thomas Petazzoni --- arch/sh/mm/gup.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/sh/mm/gup.c b/arch/sh/mm/gup.c index 56c86ca98ecfe7..075c8efe6c1d72 100644 --- a/arch/sh/mm/gup.c +++ b/arch/sh/mm/gup.c @@ -234,6 +234,9 @@ int get_user_pages_fast(unsigned long start, int nr_pages, int write, if (end < start) goto slow_irqon; + if (IS_ENABLED(CONFIG_SMP)) + goto slow_irqon; + local_irq_disable(); pgdp = pgd_offset(mm, addr); do {