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perf: Fix task_function_call() error handling
[ Upstream commit6d6b8b9f4f
] The error handling introduced by commit:2ed6edd33a
("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:2ed6edd33a
("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>
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c36782a0c9
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1 changed files with 3 additions and 2 deletions
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@ -98,7 +98,7 @@ static void remote_function(void *data)
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* retry due to any failures in smp_call_function_single(), such as if the
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* task_cpu() goes offline concurrently.
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*
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* returns @func return value or -ESRCH when the process isn't running
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* returns @func return value or -ESRCH or -ENXIO when the process isn't running
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*/
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static int
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task_function_call(struct task_struct *p, remote_function_f func, void *info)
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@ -114,7 +114,8 @@ task_function_call(struct task_struct *p, remote_function_f func, void *info)
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for (;;) {
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ret = smp_call_function_single(task_cpu(p), remote_function,
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&data, 1);
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ret = !ret ? data.ret : -EAGAIN;
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if (!ret)
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ret = data.ret;
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if (ret != -EAGAIN)
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break;
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