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authorSiarhei Liakh <Siarhei.Liakh@concurrent-rt.com>2018-06-14 21:36:07 +0200
committerThomas Gleixner <tglx@linutronix.de>2018-06-20 11:44:56 +0200
commit3ae6295ccb7cf6d344908209701badbbbb503e40 (patch)
tree8c78733ff8b5fc228c089deb4002e90b70e6f781 /arch
parentx86/intel_rdt: Enable CMT and MBM on new Skylake stepping (diff)
downloadlinux-3ae6295ccb7cf6d344908209701badbbbb503e40.tar.xz
linux-3ae6295ccb7cf6d344908209701badbbbb503e40.zip
x86: Call fixup_exception() before notify_die() in math_error()
fpu__drop() has an explicit fwait which under some conditions can trigger a fixable FPU exception while in kernel. Thus, we should attempt to fixup the exception first, and only call notify_die() if the fixup failed just like in do_general_protection(). The original call sequence incorrectly triggers KDB entry on debug kernels under particular FPU-intensive workloads. Andy noted, that this makes the whole conditional irq enable thing even more inconsistent, but fixing that it outside the scope of this. Signed-off-by: Siarhei Liakh <siarhei.liakh@concurrent-rt.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Andy Lutomirski <luto@kernel.org> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: "Borislav Petkov" <bpetkov@suse.de> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/DM5PR11MB201156F1CAB2592B07C79A03B17D0@DM5PR11MB2011.namprd11.prod.outlook.com
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kernel/traps.c14
1 files changed, 8 insertions, 6 deletions
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 03f3d7695dac..162a31d80ad5 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -834,16 +834,18 @@ static void math_error(struct pt_regs *regs, int error_code, int trapnr)
char *str = (trapnr == X86_TRAP_MF) ? "fpu exception" :
"simd exception";
- if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, SIGFPE) == NOTIFY_STOP)
- return;
cond_local_irq_enable(regs);
if (!user_mode(regs)) {
- if (!fixup_exception(regs, trapnr)) {
- task->thread.error_code = error_code;
- task->thread.trap_nr = trapnr;
+ if (fixup_exception(regs, trapnr))
+ return;
+
+ task->thread.error_code = error_code;
+ task->thread.trap_nr = trapnr;
+
+ if (notify_die(DIE_TRAP, str, regs, error_code,
+ trapnr, SIGFPE) != NOTIFY_STOP)
die(str, regs, error_code);
- }
return;
}