From: "Li,Rongqing" <lirongqing@baidu.com>
To: David Laight <david.laight.linux@gmail.com>,
Oleg Nesterov <oleg@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Borislav Petkov <bp@alien8.de>,
"Dave Hansen" <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Steven Rostedt <rostedt@goodmis.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"x86@kernel.org" <x86@kernel.org>
Subject: 答复: [SPAM] [????] Re: [PATCH] x86/math64: handle #DE in mul_u64_u64_div_u64()
Date: Tue, 22 Jul 2025 02:09:04 +0000 [thread overview]
Message-ID: <d171fbe778f046b296618f21219078b0@baidu.com> (raw)
> Even for the scheduler that recently trapped here, the 64bit sum was about the
> wrap and the very small value returned then almost certainly wouldn't have
> been handled correctly.
> (So that code needs fixing anyway to avoid the overflow.)
There are currently two bugs. The one Oleg is fixing is a crash bug in the x86-64 mul_u64_u64_div_u64() function caused by potential overflow. The mul_u64_u64_div_u64() function is used not only in cputime.c ,but also widely used within drivers.
The other one is a thread group statistics time overflow bug. If the overflow of mul_u64_u64_div_u64() can be fixed, it at least doesn't crash the system anymore. However, regarding the accuracy of the timing statistics, this bug might be more harder to fix.
-Li
reply other threads:[~2025-07-22 2:10 UTC|newest]
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