On Fri, Apr 20, 2018 at 05:08:23PM +0300, Andrey Ryabinin wrote: > > > On 04/19/2018 06:01 AM, Fengguang Wu wrote: > > Hello, > > > > FYI this happens in mainline kernel 4.17.0-rc1. > > It at least dates back to v4.8 . > > > > [ 25.697463] > > [ 25.697463] Start testing find_bit() with random-filled bitmap > > [ 25.736615] find_next_bit: 30203201 ns, 163965 iterations > > [ 25.783266] find_next_zero_bit: 45554622 ns, 163716 iterations > > [ 25.832480] find_last_bit: 48003878 ns, 163965 iterations > > [ 52.050031] watchdog: BUG: soft lockup - CPU#0 stuck for 22s! > > [swapper/0:1] > > [ 52.050031] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.17.0-rc1 #210 > > [ 52.050031] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS > > 1.10.2-1 04/01/2014 > > [ 52.050031] RIP: 0010:__sanitizer_cov_trace_pc+0x65/0x66: > > __sanitizer_cov_trace_pc at > > kernel/kcov.c:111 > > [ 52.050031] RSP: 0000:ffff88000fd43e40 EFLAGS: 00000246 ORIG_RAX: > > ffffffffffffff13 > > [ 52.050031] RAX: 0000000000000000 RBX: 0000000000000000 RCX: > > 0000000000000017 > > [ 52.050031] RDX: 0000000000000000 RSI: ffff88000fd3e000 RDI: > > 0000000000000002 > > [ 52.050031] RBP: 0000000000050000 R08: 0000000000000008 R09: > > 0000000000000000 > > [ 52.050031] R10: ffff88000fd3e000 R11: 00000000222e2c32 R12: > > ffffffff85565d90 > > [ 52.050031] R13: 0000000000030f80 R14: 0000000000030f80 R15: > > 0000000000000000 > > [ 52.050031] FS: 0000000000000000(0000) GS:ffff88001f600000(0000) > > knlGS:0000000000000000 > > [ 52.050031] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > [ 52.050031] CR2: 0000000000000000 CR3: 0000000003c6a000 CR4: > > 00000000000006b0 > > [ 52.050031] Call Trace: > > [ 52.050031] find_first_bit+0x66/0x7c: > > find_first_bit at > > lib/find_bit.c:106 (discriminator 1) > > [ 52.050031] test_find_first_bit+0x3a/0x93 > > > I suppose test_find_first_bit() needs a little more than zero cond_resched() > calls.
Or just decrease length of bitmap in this test. find_first_bit() takes lion's share of time of the test. Start testing find_bit() with random-filled bitmap find_next_bit: 240043 cycles, 164062 iterations find_next_zero_bit: 312848 cycles, 163619 iterations find_last_bit: 193748 cycles, 164062 iterations find_first_bit: 177720874 cycles, 164062 iterations I'll test the patch and send it soon if you OK with it. Yury
