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x86/pkeys/selftests: Avoid printf-in-signal deadlocks

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printf() and friends are unusable in signal handlers.  They deadlock.
The pkey selftest does not do any normal printing in signal handlers,
only extra debugging.  So, just print the format string so we get
*some* output when debugging.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellermen <mpe@ellerman.id.au>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ram Pai <linuxram@us.ibm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20180509171344.C53FD2F3@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Dave Hansen 2018-05-09 10:13:44 -07:00 committed by Ingo Molnar
parent a50093d604
commit caf9eb6b4c
1 changed files with 8 additions and 12 deletions
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20
tools/testing/selftests/x86/pkey-helpers.h
View file

@ -26,30 +26,26 @@ static inline void sigsafe_printf(const char *format, ...)
{
va_list ap;
va_start(ap, format);
if (!dprint_in_signal) {
va_start(ap, format);
vprintf(format, ap);
va_end(ap);
} else {
int ret;
int len = vsnprintf(dprint_in_signal_buffer,
DPRINT_IN_SIGNAL_BUF_SIZE,
format, ap);
/*
* len is amount that would have been printed,
* but actual write is truncated at BUF_SIZE.
* No printf() functions are signal-safe.
* They deadlock easily. Write the format
* string to get some output, even if
* incomplete.
*/
if (len > DPRINT_IN_SIGNAL_BUF_SIZE)
len = DPRINT_IN_SIGNAL_BUF_SIZE;
ret = write(1, dprint_in_signal_buffer, len);
ret = write(1, format, strlen(format));
if (ret < 0)
abort();
exit(1);
}
va_end(ap);
}
#define dprintf_level(level, args...) do { \
if (level <= DEBUG_LEVEL) \
sigsafe_printf(args); \
fflush(NULL); \
} while (0)
#define dprintf0(args...) dprintf_level(0, args)
#define dprintf1(args...) dprintf_level(1, args)