Messages in this thread | | | Subject | Re: [PATCH] arch/sh: use slow path for get_user_pages_fast() on SMP | From | Sergei Shtylyov <> | Date | Fri, 15 Jun 2018 19:04:45 +0300 |
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Hello!
On 06/15/2018 06:52 PM, Thomas Petazzoni wrote:
> 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 ^^^^ of? Else it sounds a bit tautological...
> 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 <thomas.petazzoni@bootlin.com> [...]
MBR, Sergei
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