musl - Question about SIGTIMER in musl

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Message-ID: <tencent_6AA362284986B012F97905C28CD39DE96806@qq.com>
Date: Tue, 19 Nov 2024 10:42:43 +0800
From: "AK47" <250200715@...com>
To: "musl" <musl@...ts.openwall.com>
Subject: Question about SIGTIMER in musl

Hi
&nbsp; &nbsp; We found a problem. The bottom-layer logic creates a timing thread through timer_create, but the upper-layer user is unaware of this behavior and reset the signal mask of this thread which will unmask 32 signal. As a result, the process will exit unexpectly.
&nbsp; &nbsp; The signal 32(SIGTIMER) will only used in musl timer and block for the SIGEV_THREAD. I think it can be seen as a special internal signal like 34. But in sigprocmask and pthread_sigmask, musl lacks protection for this signal. Users can modify the shielding status of such signals. Like in android, there is a function "filter_reserved_signals" used in sigprocmask to protect the internal signals state from being modified.
&nbsp; &nbsp; Considering that upper-layer users may not know the signal 32 has been blocked, should we add a default block for SIGTIMER in pthread_sigmask like android? Or is there other considerations?

Best
Li
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