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powerpc/rtas: rtas_ibm_suspend_me -> rtas_ibm_suspend_me_unsafe

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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>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201207215200.1785968-4-nathanl@linux.ibm.com
This commit is contained in:
Nathan Lynch
2020-12-07 15:51:35 -06:00
committed by Michael Ellerman
parent 970e453ea4
commit 7049b288ea
3 changed files with 5 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
arch/powerpc/include/asm/rtas.h
View File

@ -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 void rtas_progress(char *s, unsigned short hex);
extern int rtas_suspend_cpu(struct rtas_suspend_me_data *data); 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_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; struct rtc_time;
extern time64_t rtas_get_boot_time(void); extern time64_t rtas_get_boot_time(void);

6
arch/powerpc/kernel/rtas.c
View File

@ -843,7 +843,7 @@ static void rtas_percpu_suspend_me(void *info)
__rtas_suspend_cpu((struct rtas_suspend_me_data *)info, 1); __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 state;
long rc; long rc;
@ -949,7 +949,7 @@ int rtas_call_reentrant(int token, int nargs, int nret, int *outputs, ...)
} }
#else /* CONFIG_PPC_PSERIES */ #else /* CONFIG_PPC_PSERIES */
int rtas_ibm_suspend_me(u64 handle) int rtas_ibm_suspend_me_unsafe(u64 handle)
{ {
return -ENOSYS; return -ENOSYS;
} }
@ -1185,7 +1185,7 @@ SYSCALL_DEFINE1(rtas, struct rtas_args __user *, uargs)
int rc = 0; int rc = 0;
u64 handle = ((u64)be32_to_cpu(args.args[0]) << 32) u64 handle = ((u64)be32_to_cpu(args.args[0]) << 32)
| be32_to_cpu(args.args[1]); | be32_to_cpu(args.args[1]);
rc = rtas_ibm_suspend_me(handle); rc = rtas_ibm_suspend_me_unsafe(handle);
if (rc == -EAGAIN) if (rc == -EAGAIN)
args.rets[0] = cpu_to_be32(RTAS_NOT_SUSPENDABLE); args.rets[0] = cpu_to_be32(RTAS_NOT_SUSPENDABLE);
else if (rc == -EIO) else if (rc == -EIO)

2
arch/powerpc/platforms/pseries/mobility.c
View File

@ -370,7 +370,7 @@ static ssize_t migration_store(struct class *class,
return rc; return rc;
do { do {
rc = rtas_ibm_suspend_me(streamid); rc = rtas_ibm_suspend_me_unsafe(streamid);
if (rc == -EAGAIN) if (rc == -EAGAIN)
ssleep(1); ssleep(1);
} while (rc == -EAGAIN); } while (rc == -EAGAIN);