rseq/cleanup: Do not abort rseq c.s. in child on fork()

compudj · Ingo Molnar · commit 9a789fcfe860 · 2018-06-21T12:40:13.000+02:00
Considering that we explicitly forbid system calls in rseq critical sections, it is not valid to issue a fork or clone system call within a rseq critical section, so rseq_fork() is not required to restart an active rseq c.s. in the child process. Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Ben Maurer <bmaurer@fb.com> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Chris Lameter <cl@linux.com> Cc: Dave Watson <davejwatson@fb.com> Cc: Joel Fernandes <joelaf@google.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: Paul E . McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul Turner <pjt@google.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Russell King <linux@arm.linux.org.uk> Cc: Shuah Khan <shuahkh@osg.samsung.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Will Deacon <will.deacon@arm.com> Cc: linux-api@vger.kernel.org Cc: linux-kselftest@vger.kernel.org Link: https://lore.kernel.org/lkml/20180619133230.4087-4-mathieu.desnoyers@efficios.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/include/linux/sched.h b/include/linux/sched.h
@@ -1831,9 +1831,7 @@ static inline void rseq_migrate(struct task_struct *t)
 
 /*
  * If parent process has a registered restartable sequences area, the
- * child inherits. Only applies when forking a process, not a thread. In
- * case a parent fork() in the middle of a restartable sequence, set the
- * resume notifier to force the child to retry.
+ * child inherits. Only applies when forking a process, not a thread.
  */
 static inline void rseq_fork(struct task_struct *t, unsigned long clone_flags)
 {
@@ -1847,7 +1845,6 @@ static inline void rseq_fork(struct task_struct *t, unsigned long clone_flags)
 		t->rseq_len = current->rseq_len;
 		t->rseq_sig = current->rseq_sig;
 		t->rseq_event_mask = current->rseq_event_mask;
-		rseq_preempt(t);
 	}
 }
 

Original file line number	Diff line number	Diff line change
`@@ -1831,9 +1831,7 @@ static inline void rseq_migrate(struct task_struct *t)`
`1831`	`1831`
`1832`	`1832`	`/*`
`1833`	`1833`	`* If parent process has a registered restartable sequences area, the`
`1834`		`- * child inherits. Only applies when forking a process, not a thread. In`
`1835`		`- * case a parent fork() in the middle of a restartable sequence, set the`
`1836`		`- * resume notifier to force the child to retry.`
	`1834`	`+ * child inherits. Only applies when forking a process, not a thread.`
`1837`	`1835`	`*/`
`1838`	`1836`	`static inline void rseq_fork(struct task_struct *t, unsigned long clone_flags)`
`1839`	`1837`	`{`
`@@ -1847,7 +1845,6 @@ static inline void rseq_fork(struct task_struct *t, unsigned long clone_flags)`
`1847`	`1845`	`t->rseq_len = current->rseq_len;`
`1848`	`1846`	`t->rseq_sig = current->rseq_sig;`
`1849`	`1847`	`t->rseq_event_mask = current->rseq_event_mask;`
`1850`		`- rseq_preempt(t);`
`1851`	`1848`	`}`
`1852`	`1849`	`}`
`1853`	`1850`