On 8/30/2018 7:22 AM, Andrew Morton Wrote: > On Tue, 28 Aug 2018 12:20:46 +0800 Jia He <hejianet@xxxxxxxxx> wrote: > >> Hi Andrew >> FYI,I watched a lockdep warning based on your mmotm master branch[1] > > Thanks. We'll need help from ARM peeps on this please. > >> [ 6.692731] ------------[ cut here ]------------ >> [ 6.696391] DEBUG_LOCKS_WARN_ON(!current->hardirqs_enabled) >> [ 6.696404] WARNING: CPU: 3 PID: 320 at kernel/locking/lockdep.c:3845 >> check_flags.part.38+0x9c/0x16c >> [ 6.711082] Modules linked in: >> [ 6.714101] CPU: 3 PID: 320 Comm: modprobe Not tainted 4.18.0-rc4-mm1+ #56 >> [ 6.720956] Hardware name: WIWYNN HXT REP-1 System H001-00001-0/HXT REP-1 >> CRB, BIOS 0ACJA530 03/20/2018 >> [ 6.730332] pstate: 60400085 (nZCv daIf +PAN -UAO) >> [ 6.735106] pc : check_flags.part.38+0x9c/0x16c >> [ 6.739619] lr : check_flags.part.38+0x9c/0x16c >> [ 6.744133] sp : ffff80178536fbf0 >> [ 6.747432] x29: ffff80178536fbf0 x28: ffff8017905a1b00 >> [ 6.752727] x27: 0000000000000002 x26: 0000000000000000 >> [ 6.758022] x25: ffff000008abeb14 x24: 0000000000000000 >> [ 6.763317] x23: 0000000000000001 x22: 0000000000000001 >> [ 6.768612] x21: 0000000000000001 x20: 0000000000000000 >> [ 6.773908] x19: ffff00000a041000 x18: 0000000000000000 >> [ 6.779202] x17: 0000000000000000 x16: 0000000000000000 >> [ 6.784498] x15: 0000000000000000 x14: 0000000000000000 >> [ 6.789793] x13: ffff000008d6b190 x12: 752ce9eb60de3f00 >> [ 6.795088] x11: ffff80178536f7f0 x10: ffff80178536f7f0 >> [ 6.800383] x9 : 00000000ffffffd0 x8 : 0000000000000000 >> [ 6.805678] x7 : ffff00000816fe48 x6 : ffff801794ba62b8 >> [ 6.810973] x5 : 0000000000000000 x4 : 0000000000000000 >> [ 6.816269] x3 : ffffffffffffffff x2 : ffff0000091ed988 >> [ 6.821564] x1 : 752ce9eb60de3f00 x0 : 752ce9eb60de3f00 >> [ 6.826859] Call trace: >> [ 6.829290] check_flags.part.38+0x9c/0x16c >> [ 6.833457] lock_acquire+0x12c/0x280 >> [ 6.837104] down_read_trylock+0x78/0x98 >> [ 6.841011] do_page_fault+0x150/0x480 >> [ 6.844742] do_translation_fault+0x74/0x80 >> [ 6.848909] do_mem_abort+0x60/0x108 >> [ 6.852467] el0_da+0x24/0x28 >> [ 6.855418] irq event stamp: 250 >> [ 6.858633] hardirqs last enabled at (249): [<ffff00000830e518>] >> mem_cgroup_commit_charge+0x9c/0x13c >> [ 6.867833] hardirqs last disabled at (250): [<ffff000008095f40>] >> el0_svc_handler+0xc4/0x16c >> [ 6.876252] softirqs last enabled at (242): [<ffff000008081c48>] >> __do_softirq+0x2f8/0x554 >> [ 6.884501] softirqs last disabled at (229): [<ffff0000080f1bec>] >> irq_exit+0x180/0x194 >> [ 6.892399] ---[ end trace b45768f94a7b7d9f ]--- >> [ 6.896998] possible reason: unannotated irqs-on. >> [ 6.901685] irq event stamp: 250 >> [ 6.904898] hardirqs last enabled at (249): [<ffff00000830e518>] >> mem_cgroup_commit_charge+0x9c/0x13c >> [ 6.914100] hardirqs last disabled at (250): [<ffff000008095f40>] >> el0_svc_handler+0xc4/0x16c >> [ 6.922519] softirqs last enabled at (242): [<ffff000008081c48>] >> __do_softirq+0x2f8/0x554 >> [ 6.930766] softirqs last disabled at (229): [<ffff0000080f1bec>] >> irq_exit+0x180/0x194 >> [ 7.023827] Initialise system trusted keyrings >> [ 7.027414] workingset: timestamp_bits=45 max_order=25 bucket_order=0 > > Lockdep says current->hardirqs_enabled is false and that is indeed an > error. arch/arm64/kernel/entry.S:el0_da does enable_daif which might > be an attempt to enable hardirqs, but how does that get propagated into > lockdep's ->hardirqs_enabled? By calling > local_irq_enable()->trace_hardirqs_on(), but that's C, not assembler. > > And what changed to cause this? > > I dunno anything. Help! > >> I thought the root cause might be at [2] which seems not in your branch yet. >> >> [1] http://git.cmpxchg.org/cgit.cgi/linux-mmotm.git >> [2] >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit?id=efd112 > > I agree, that doesn't look like the culprit. But something may well > have gone wrong in "the recent conversion of the syscall entry/exit > code to C". Sorry for my unclearly previously description. 1. no such lockdep warning in latest mainline kernel git tree. 2. there is a 100% producible warning based on your latest mmotm tree 3. after applying the commit efd112 based on your mmotm tree, the warning disappearred I will do some further digging to answer your question if no other experts' help -- Cheers, Jia
