From: Steven Rostedt Date: Wed, 25 May 2016 17:47:26 +0000 (-0400) Subject: x86/paravirt: Do not trace _paravirt_ident_*() functions X-Git-Tag: v3.2.84~63 X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=commitdiff_plain;h=51017990da152ae5e9bd9edba20f709a7211623e x86/paravirt: Do not trace _paravirt_ident_*() functions commit 15301a570754c7af60335d094dd2d1808b0641a5 upstream. Łukasz Daniluk reported that on a RHEL kernel that his machine would lock up after enabling function tracer. I asked him to bisect the functions within available_filter_functions, which he did and it came down to three: _paravirt_nop(), _paravirt_ident_32() and _paravirt_ident_64() It was found that this is only an issue when noreplace-paravirt is added to the kernel command line. This means that those functions are most likely called within critical sections of the funtion tracer, and must not be traced. In newer kenels _paravirt_nop() is defined within gcc asm(), and is no longer an issue. But both _paravirt_ident_{32,64}() causes the following splat when they are traced: mm/pgtable-generic.c:33: bad pmd ffff8800d2435150(0000000001d00054) mm/pgtable-generic.c:33: bad pmd ffff8800d3624190(0000000001d00070) mm/pgtable-generic.c:33: bad pmd ffff8800d36a5110(0000000001d00054) mm/pgtable-generic.c:33: bad pmd ffff880118eb1450(0000000001d00054) NMI watchdog: BUG: soft lockup - CPU#2 stuck for 22s! [systemd-journal:469] Modules linked in: e1000e CPU: 2 PID: 469 Comm: systemd-journal Not tainted 4.6.0-rc4-test+ #513 Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v02.05 05/07/2012 task: ffff880118f740c0 ti: ffff8800d4aec000 task.ti: ffff8800d4aec000 RIP: 0010:[] [] queued_spin_lock_slowpath+0x118/0x1a0 RSP: 0018:ffff8800d4aefb90 EFLAGS: 00000246 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff88011eb16d40 RDX: ffffffff82485760 RSI: 000000001f288820 RDI: ffffea0000008030 RBP: ffff8800d4aefb90 R08: 00000000000c0000 R09: 0000000000000000 R10: ffffffff821c8e0e R11: 0000000000000000 R12: ffff880000200fb8 R13: 00007f7a4e3f7000 R14: ffffea000303f600 R15: ffff8800d4b562e0 FS: 00007f7a4e3d7840(0000) GS:ffff88011eb00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f7a4e3f7000 CR3: 00000000d3e71000 CR4: 00000000001406e0 Call Trace: _raw_spin_lock+0x27/0x30 handle_pte_fault+0x13db/0x16b0 handle_mm_fault+0x312/0x670 __do_page_fault+0x1b1/0x4e0 do_page_fault+0x22/0x30 page_fault+0x28/0x30 __vfs_read+0x28/0xe0 vfs_read+0x86/0x130 SyS_read+0x46/0xa0 entry_SYSCALL_64_fastpath+0x1e/0xa8 Code: 12 48 c1 ea 0c 83 e8 01 83 e2 30 48 98 48 81 c2 40 6d 01 00 48 03 14 c5 80 6a 5d 82 48 89 0a 8b 41 08 85 c0 75 09 f3 90 8b 41 08 <85> c0 74 f7 4c 8b 09 4d 85 c9 74 08 41 0f 18 09 eb 02 f3 90 8b Reported-by: Łukasz Daniluk Signed-off-by: Steven Rostedt Signed-off-by: Linus Torvalds Signed-off-by: Ben Hutchings --- diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c index af5b675c7f68..d21b32eeaa59 100644 --- a/arch/x86/kernel/paravirt.c +++ b/arch/x86/kernel/paravirt.c @@ -52,12 +52,12 @@ asm (".pushsection .entry.text, \"ax\"\n" ".popsection"); /* identity function, which can be inlined */ -u32 _paravirt_ident_32(u32 x) +u32 notrace _paravirt_ident_32(u32 x) { return x; } -u64 _paravirt_ident_64(u64 x) +u64 notrace _paravirt_ident_64(u64 x) { return x; }