From: "Leizhen (ThunderTown)" <thunder.leizhen@huawei.com>
To: Will Deacon <will@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Russell King <linux@armlinux.org.uk>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Cc: Wang Nan <wangnan0@huawei.com>
Subject: Re: [PATCH 1/1] ARM: hw_breakpoint: Do not directly check the event's overflow_handler hook
Date: Sun, 7 Feb 2021 21:05:36 +0800 [thread overview]
Message-ID: <baea47e7-1062-e39b-d642-b7147aa3dcfe@huawei.com> (raw)
In-Reply-To: <20210207105934.2001-1-thunder.leizhen@huawei.com>
On 2021/2/7 18:59, Zhen Lei wrote:
> The commit 1879445dfa7b ("perf/core: Set event's default
> ::overflow_handler()") set a default event->overflow_handler in
> perf_event_alloc(), and replace the check event->overflow_handler with
> is_default_overflow_handler(), but one is missing.
>
> Currently, the bp->overflow_handler can not be NULL. As a result,
> enable_single_step() is always not invoked.
Our test case use "perf record -e mem:$TEST_LOC_ADDR:x -p $TEST_PID sleep 10" to track
the invocation of a test function, the entry address of the function is $TEST_LOC_ADDR.
This function was called only once. Therefore, the sampling result of perf should be one，
as follow:
[ perf record: Captured and wrote 0.001 MB perf.data (1 samples) ]
But it's actually infinite.
[ perf record: Captured and wrote 135.426 MB perf.data (2068004 samples) ]
If sleep 10 is not specified, OOM will be reported.
>
> Fixes: 1879445dfa7b ("perf/core: Set event's default ::overflow_handler()")
> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
> Cc: Wang Nan <wangnan0@huawei.com>
> ---
> arch/arm/kernel/hw_breakpoint.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c
> index 08660ae9dcbce1c..b1423fb130ea4a0 100644
> --- a/arch/arm/kernel/hw_breakpoint.c
> +++ b/arch/arm/kernel/hw_breakpoint.c
> @@ -886,7 +886,7 @@ static void breakpoint_handler(unsigned long unknown, struct pt_regs *regs)
> info->trigger = addr;
> pr_debug("breakpoint fired: address = 0x%x\n", addr);
> perf_bp_event(bp, regs);
> - if (!bp->overflow_handler)
> + if (is_default_overflow_handler(bp))
> enable_single_step(bp, addr);
> goto unlock;
> }
>
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next prev parent reply other threads:[~2021-02-07 13:07 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-07 10:59 [PATCH 1/1] ARM: hw_breakpoint: Do not directly check the event's overflow_handler hook Zhen Lei
2021-02-07 13:05 ` Leizhen (ThunderTown) [this message]
2021-02-12 10:02 ` Will Deacon
2021-02-18 2:03 ` Leizhen (ThunderTown)
2021-02-18 9:13 ` Will Deacon
2021-02-18 10:56 ` Leizhen (ThunderTown)
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