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<pre style="overflow-wrap: break-word; margin: 0em;"><span style="white-space: pre-wrap; text-decoration-style: initial; text-decoration-color: initial;"><font color="#a01e1e" face="courier, courier new, monospace"><b>We also found that it is easy to cause deadlock in the kswap scene， We observed the following deadlock in the stress test under low
memory scenario，</b></font></span><span style="font-family: courier, "courier new", monospace; white-space: pre-wrap; color: rgb(160, 30, 30);"> <b></b></span><font color="#a01e1e" face="courier, courier new, monospace"><span style="white-space: pre-wrap;"><b>Same as "erofs: fix deadlock when shrink erofs slab".</b></span></font></pre>
<pre style="overflow-wrap: break-word; margin: 0em;"><font color="#a01e1e" face="courier, courier new, monospace"><span style="white-space: pre-wrap;"><b><br></b></span></font></pre>
<pre style="overflow-wrap: break-word; margin: 0em;"><p class="MsoNormal" style="margin: 0in; font-size: 11pt; font-family: Calibri, sans-serif; white-space: normal;"><span style="font-size: 9pt;">Thread A: <o:p></o:p></span><span style="font-size: 9pt; background-color: transparent;">Thread B:</span></p><p class="MsoNormal" style="margin: 0in; font-size: 11pt; font-family: Calibri, sans-serif; white-space: normal;"><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;">erofs_try_to_release_workgroup(</span><span style="background-color: transparent; font-size: 12px; color: rgb(112, 173, 71);">grp = 0xFFFFFF87ADFEE610</span><span style="background-color: transparent; font-size: 12px;">)</span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-size: 9pt;">erofs_insert_workgroup()</span></p><p class="MsoNormal" style="margin: 0in; font-size: 11pt; font-family: Calibri, sans-serif; white-space: normal;"><span style="font-size: 9pt;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;">erofs_workgroup_try_to_freeze(grp, 1)</span><span style="background-color: transparent; font-size: 9pt;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="background-color: transparent; font-size: 9pt;">//xa lock is held here</span></p><p class="MsoNormal" style="margin: 0in; font-size: 11pt; font-family: Calibri, sans-serif; white-space: normal;"><span style="font-size: 9pt;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;">//set ref count to EROFS_LOCKED_MAGIC</span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-size: 9pt;">xa_lock(&sbi->managed_pslots);</span></p><p class="MsoNormal" style="margin: 0in; font-size: 11pt; font-family: Calibri, sans-serif; white-space: normal;"><span style="font-size: 9pt;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;">atomic_cmpxchg(&grp->refcount, val,</span><span style="background-color: transparent; font-size: 12px;"> </span><span style="background-color: transparent; font-size: 12px; color: red;">EROFS_LOCKED_MAGIC</span><span style="background-color: transparent; font-size: 12px;">)</span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-size: 9pt;">pre = __xa_cmpxchg(&sbi->managed_pslots, grp->index, NULL, grp, GFP_NOFS);</span></p><p class="MsoNormal" style="margin: 0in; font-size: 11pt; font-family: Calibri, sans-serif; white-space: normal;"><span style="font-size: 9pt;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;">xa_erase(&sbi->managed_pslots, grp->index)</span><span style="background-color: transparent; font-size: 12px;"> </span><span style="background-color: transparent; font-size: 9pt;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-size: 9pt;">erofs_workgroup_get(pre) //</span><span style="background-color: transparent; font-size: 9pt; color: rgb(112, 173, 71);">pre = grp = 0xFFFFFF87ADFEE610</span><span style="background-color: transparent; font-size: 9pt;"> </span></p><p class="MsoNormal" style="margin: 0in; font-size: 11pt; font-family: Calibri, sans-serif; white-space: normal;"><span style="font-size: 9pt;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;">//stuck there to wait for xa lock, already held by thread B</span><span style="background-color: transparent; font-size: 9pt;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="background-color: transparent; font-size: 9pt;">erofs_wait_on_workgroup_freezed(grp);</span></p><p class="MsoNormal" style="margin: 0in; font-size: 11pt; font-family: Calibri, sans-serif; white-space: normal;"><span style="font-size: 9pt;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;">xa_lock(xa); </span><span style="background-color: transparent; font-size: 9pt;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="background-color: transparent; font-family: "Microsoft YaHei UI"; font-size: 14px;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="background-color: transparent; font-size: 9pt;">//wait ref count to be unlocked, which should be done by thread A</span></p><p class="MsoNormal" style="margin: 0in; font-size: 11pt; font-family: Calibri, sans-serif; white-space: normal;"><span style="font-size: 9pt;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="font-family: "Microsoft YaHei UI"; font-size: 14px; background-color: transparent;"> </span><span style="background-color: transparent; font-size: 9pt;">atomic_cond_read_relaxed(&grp->refcount, VAL != </span><span style="background-color: transparent; font-size: 8pt; color: red;">EROFS_LOCKED_MAGIC</span><span style="background-color: transparent; font-size: 8pt;">);</span></p><p class="MsoNormal" style="margin: 0in; white-space: normal;"><font color="#a01e1e" face="courier, courier new, monospace"><span style="text-decoration-style: initial; text-decoration-color: initial;"><br></span></font></p><p class="MsoNormal" style="margin: 0in;"><span style="white-space: normal; text-decoration-style: initial; text-decoration-color: initial;"><font color="#a01e1e" face="courier, courier new, monospace">Follow-up fix:</font></span><span style="color: rgb(160, 30, 30); font-family: courier, "courier new", monospace; white-space: pre-wrap; background-color: transparent;">it need to hold the xa lock before freeze the workgroup</span></p><pre style="font-family: courier, "courier new", monospace; white-space: pre-wrap; overflow-wrap: break-word; margin-top: 0px; margin-bottom: 0px; color: rgb(160, 30, 30);">beacuse we will operate xarry?</pre><p class="MsoNormal" style="margin: 0in; font-size: 11pt; font-family: Calibri, sans-serif; white-space: normal;"><span style="font-size: 9pt;"> <o:p></o:p></span></p><p class="MsoNormal" style="margin: 0in; font-size: 11pt; font-family: Calibri, sans-serif; white-space: normal;"><span style="font-size: 9pt;"> <o:p></o:p></span></p><p class="MsoNormal" style="margin: 0in; font-size: 11pt; font-family: Calibri, sans-serif; white-space: normal;"><span style="font-size: 9pt;"> <br> <o:p></o:p></span></p><p class="MsoNormal" style="margin: 0in; font-size: 11pt; font-family: Calibri, sans-serif; white-space: normal;"><span style="font-size: 9pt;"> </span></p></pre>
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