Hi Sebastian, On Fri, Mar 29, 2019 at 02:09:56PM +0100, Sebastian Andrzej Siewior wrote: > Two per-CPU variables are allocated as pointer to per-CPU memory which > then are used as scratch buffers. > We could be smart about this and use instead a per-CPU struct which > contains the pointers already and then we need to allocate just the > scratch buffers. > Add a lock to the struct. By doing so we can avoid the get_cpu() > statement and gain lockdep coverage (if enabled) to ensure that the lock > is always acquired in the right context. On non-preemptible kernels the > lock vanishes. > It is okay to use raw_cpu_ptr() in order to get a pointer to the struct > since it is protected by the spinlock. > > The diffstat of this is negative and according to size scompress.o: > text data bss dec hex filename > 1847 160 24 2031 7ef dbg_before.o > 1754 232 4 1990 7c6 dbg_after.o > 1799 64 24 1887 75f no_dbg-before.o > 1703 88 4 1795 703 no_dbg-after.o > > The overall size increase difference is also negative. The increase in > the data section is only four bytes without lockdep. > Unfortunately, this patch causes random crashes. [ 13.084225] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 [ 13.084687] Mem abort info: [ 13.084821] ESR = 0x96000044 [ 13.085008] Exception class = DABT (current EL), IL = 32 bits [ 13.085189] SET = 0, FnV = 0 [ 13.085331] EA = 0, S1PTW = 0 [ 13.085468] Data abort info: [ 13.086018] ISV = 0, ISS = 0x00000044 [ 13.086185] CM = 0, WnR = 1 [ 13.086379] [0000000000000000] user address but active_mm is swapper [ 13.087032] Internal error: Oops: 96000044 [#1] PREEMPT SMP [ 13.087322] Modules linked in: [ 13.087645] Process cryptomgr_test (pid: 165, stack limit = 0x(____ptrval____)) [ 13.088038] CPU: 1 PID: 165 Comm: cryptomgr_test Not tainted 5.1.0-rc4-next-20190410 #1 [ 13.088250] Hardware name: ZynqMP ZCU102 Rev1.0 (DT) [ 13.088530] pstate: 80000005 (Nzcv daif -PAN -UAO) [ 13.088740] pc : __memcpy+0xc0/0x180 [ 13.088887] lr : scatterwalk_copychunks+0xd4/0x1e8 [ 13.089033] sp : ffff000012f2ba50 [ 13.089139] x29: ffff000012f2ba50 x28: ffff80007a7c0500 [ 13.089324] x27: 0000000000000000 x26: ffff000012f2bae8 [ 13.089460] x25: 0000000000000046 x24: 0000000000000046 [ 13.089643] x23: ffff80007a004440 x22: 0000000000000046 [ 13.089815] x21: 0000000000000000 x20: 000081ffffffffff [ 13.089974] x19: 0000000000000000 x18: 00000000000007ff [ 13.090111] x17: 0000000000000000 x16: 0000000000000000 [ 13.090264] x15: ffff0000130ff748 x14: 0000000000000000 [ 13.090414] x13: ffff000011c509e8 x12: ffff000011a46980 [ 13.090569] x11: ffff000011a46000 x10: 0000000000000001 [ 13.090736] x9 : 0000000000000000 x8 : 20646e6120776f6e [ 13.090885] x7 : 207375206e696f4a x6 : 0000000000000000 [ 13.091022] x5 : ffff0000117bf808 x4 : 0000000000000000 [ 13.091168] x3 : 0000000000000000 x2 : ffffffffffffffc6 [ 13.091313] x1 : ffff80007a62e610 x0 : 0000000000000000 [ 13.091554] Call trace: [ 13.091682] __memcpy+0xc0/0x180 [ 13.091810] scatterwalk_map_and_copy+0x88/0xf0 [ 13.091956] scomp_acomp_comp_decomp+0x94/0x140 [ 13.092083] scomp_acomp_compress+0x10/0x18 [ 13.092201] test_acomp+0x158/0x5c0 [ 13.092307] alg_test_comp+0x298/0x440 [ 13.092420] alg_test.part.8+0xbc/0x398 [ 13.092542] alg_test+0x3c/0x68 [ 13.092642] cryptomgr_test+0x44/0x50 [ 13.092754] kthread+0x128/0x130 [ 13.092867] ret_from_fork+0x10/0x18 [ 13.093158] Code: 14000028 f1020042 5400024a a8c12027 (a88120c7) This is seen with an arm64 image running on qemu with machine xlnx-zcu102 and two CPUs, and crypto test options enabled. It happens roughly every other boot. Reverting the patch fixes the problem. Bisect log (from crypto/master) is attached. Guenter --- # bad: [eda69b0c06bc615f4b055d560ed19001619e611a] crypto: testmgr - add panic_on_fail module parameter # good: [9e98c678c2d6ae3a17cb2de55d17f69dddaa231b] Linux 5.1-rc1 git bisect start 'HEAD' 'v5.1-rc1' # good: [52c899ec472e88e33c31c33bea844217c0963a05] crypto: ccp - Make ccp_register_rsa_alg static git bisect good 52c899ec472e88e33c31c33bea844217c0963a05 # good: [6a4d1b18ef00a7b182740b7b4d8a0fcd317368f8] crypto: scompress - return proper error code for allocation failure git bisect good 6a4d1b18ef00a7b182740b7b4d8a0fcd317368f8 # bad: [307508d1072979f4435416f87936f87eaeb82054] crypto: crct10dif-generic - fix use via crypto_shash_digest() git bisect bad 307508d1072979f4435416f87936f87eaeb82054 # bad: [8316da02e3e07b0da9b2d812a619b5513c7f59d2] crypto: ccp - Use kmemdup in ccp_copy_and_save_keypart() git bisect bad 8316da02e3e07b0da9b2d812a619b5513c7f59d2 # bad: [61abc356bf310d346d2d469cb009f6d4334f34de] crypto: aes - Use ___cacheline_aligned for aes data git bisect bad 61abc356bf310d346d2d469cb009f6d4334f34de # bad: [71052dcf4be70be4077817297dcde7b155e745f2] crypto: scompress - Use per-CPU struct instead multiple variables git bisect bad 71052dcf4be70be4077817297dcde7b155e745f2 # first bad commit: [71052dcf4be70be4077817297dcde7b155e745f2] crypto: scompress - Use per-CPU struct instead multiple variables
