Commit 6d6b8b9f authored by Kajol Jain's avatar Kajol Jain Committed by Ingo Molnar

perf: Fix task_function_call() error handling

The error handling introduced by commit:

  2ed6edd3 ("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: 2ed6edd3 ("perf: Add cond_resched() to task_function_call()")
Reported-by: default avatarSrikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: default avatarKajol Jain <kjain@linux.ibm.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Reviewed-by: default avatarBarret Rhoden <brho@google.com>
Tested-by: default avatarSrikar Dronamraju <srikar@linux.vnet.ibm.com>
Link: https://lkml.kernel.org/r/20200827064732.20860-1-kjain@linux.ibm.com
parent c85fb28b
......@@ -99,7 +99,7 @@ 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)
......@@ -115,7 +115,8 @@ 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;
......
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