Commit 80e745b6 authored Aug 27, 2020 by Kajol Jain Committed by Greg Kroah-Hartman Oct 14, 2020

perf: Fix task_function_call() error handling



[ Upstream commit 6d6b8b9f4fceab7266ca03d194f60ec72bd4b654 ]

The error handling introduced by commit:

  2ed6edd33a21 ("perf: Add cond_resched() to task_function_call()")

looses any return value from smp_call_function_single() that is not
{0, -EINVAL}. This is a problem because it will return -EXNIO when the
target CPU is offline. Worse, in that case it'll turn into an infinite
loop.

Fixes: 2ed6edd33a21 ("perf: Add cond_resched() to task_function_call()")
Reported-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Barret Rhoden <brho@google.com>
Tested-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Link: https://lkml.kernel.org/r/20200827064732.20860-1-kjain@linux.ibm.com


Signed-off-by: Sasha Levin <sashal@kernel.org>

parent 4b00aa56

kernel/events/core.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -98,7 +98,7 @@ static void remote_function(void *data)
		* retry due to any failures in smp_call_function_single(), such as if the
		* task_cpu() goes offline concurrently.
		*
		* returns @func return value or -ESRCH when the process isn't running
		* returns @func return value or -ESRCH or -ENXIO when the process isn't running
		*/
		static int
		task_function_call(struct task_struct p, remote_function_f func, void info)
		@@ -114,7 +114,8 @@ task_function_call(struct task_struct p, remote_function_f func, void info)
		for (;;) {
		ret = smp_call_function_single(task_cpu(p), remote_function,
		&data, 1);
		ret = !ret ? data.ret : -EAGAIN;
		if (!ret)
		ret = data.ret;

		if (ret != -EAGAIN)
		break;