[PATCH v2 03/28] powerpc/rtas: rtas_ibm_suspend_me -> rtas_ibm_suspend_me_unsafe

From: Nathan Lynch <nathanl@linux.ibm.com>
To: linuxppc-dev@lists.ozlabs.org
Cc: tyreld@linux.ibm.com, ajd@linux.ibm.com, mmc@linux.vnet.ibm.com,
	cforno12@linux.vnet.ibm.com, drt@linux.vnet.ibm.com,
	brking@linux.ibm.com
Subject: [PATCH v2 03/28] powerpc/rtas: rtas_ibm_suspend_me -> rtas_ibm_suspend_me_unsafe
Date: Mon,  7 Dec 2020 15:51:35 -0600	[thread overview]
Message-ID: <20201207215200.1785968-4-nathanl@linux.ibm.com> (raw)
In-Reply-To: <20201207215200.1785968-1-nathanl@linux.ibm.com>

The pseries partition suspend sequence requires that all active CPUs
call H_JOIN, which suspends all but one of them with interrupts
disabled. The "chosen" CPU is then to call ibm,suspend-me to complete
the suspend. Upon returning from ibm,suspend-me, the chosen CPU is to
use H_PROD to wake the joined CPUs.

Using on_each_cpu() for this, as rtas_ibm_suspend_me() does to
implement partition migration, is susceptible to deadlock with other
users of on_each_cpu() and with users of stop_machine APIs. The
callback passed to on_each_cpu() is not allowed to synchronize with
other CPUs in the way it is used here.

Complicating the fix is the fact that rtas_ibm_suspend_me() also
occupies the function name that should be used to provide a more
conventional wrapper for ibm,suspend-me. Rename rtas_ibm_suspend_me()
to rtas_ibm_suspend_me_unsafe() to free up the name and indicate that
it should not gain users.

Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
---
 arch/powerpc/include/asm/rtas.h           | 2 +-
 arch/powerpc/kernel/rtas.c                | 6 +++---
 arch/powerpc/platforms/pseries/mobility.c | 2 +-
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/include/asm/rtas.h b/arch/powerpc/include/asm/rtas.h
index f060181a0d32..8436ed01567b 100644
--- a/arch/powerpc/include/asm/rtas.h
+++ b/arch/powerpc/include/asm/rtas.h
@@ -257,7 +257,7 @@ extern int rtas_set_indicator_fast(int indicator, int index, int new_value);
 extern void rtas_progress(char *s, unsigned short hex);
 extern int rtas_suspend_cpu(struct rtas_suspend_me_data *data);
 extern int rtas_suspend_last_cpu(struct rtas_suspend_me_data *data);
-extern int rtas_ibm_suspend_me(u64 handle);
+int rtas_ibm_suspend_me_unsafe(u64 handle);
 
 struct rtc_time;
 extern time64_t rtas_get_boot_time(void);
diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
index 4ed64aba37d6..0a8e5dc2c108 100644
--- a/arch/powerpc/kernel/rtas.c
+++ b/arch/powerpc/kernel/rtas.c
@@ -843,7 +843,7 @@ static void rtas_percpu_suspend_me(void *info)
 	__rtas_suspend_cpu((struct rtas_suspend_me_data *)info, 1);
 }
 
-int rtas_ibm_suspend_me(u64 handle)
+int rtas_ibm_suspend_me_unsafe(u64 handle)
 {
 	long state;
 	long rc;
@@ -949,7 +949,7 @@ int rtas_call_reentrant(int token, int nargs, int nret, int *outputs, ...)
 }
 
 #else /* CONFIG_PPC_PSERIES */
-int rtas_ibm_suspend_me(u64 handle)
+int rtas_ibm_suspend_me_unsafe(u64 handle)
 {
 	return -ENOSYS;
 }
@@ -1185,7 +1185,7 @@ SYSCALL_DEFINE1(rtas, struct rtas_args __user *, uargs)
 		int rc = 0;
 		u64 handle = ((u64)be32_to_cpu(args.args[0]) << 32)
 		              | be32_to_cpu(args.args[1]);
-		rc = rtas_ibm_suspend_me(handle);
+		rc = rtas_ibm_suspend_me_unsafe(handle);
 		if (rc == -EAGAIN)
 			args.rets[0] = cpu_to_be32(RTAS_NOT_SUSPENDABLE);
 		else if (rc == -EIO)
diff --git a/arch/powerpc/platforms/pseries/mobility.c b/arch/powerpc/platforms/pseries/mobility.c
index 2f73cb5bf12d..6ff642e84c6a 100644
--- a/arch/powerpc/platforms/pseries/mobility.c
+++ b/arch/powerpc/platforms/pseries/mobility.c
@@ -370,7 +370,7 @@ static ssize_t migration_store(struct class *class,
 		return rc;
 
 	do {
-		rc = rtas_ibm_suspend_me(streamid);
+		rc = rtas_ibm_suspend_me_unsafe(streamid);
 		if (rc == -EAGAIN)
 			ssleep(1);
 	} while (rc == -EAGAIN);
-- 
2.28.0

